Test a number for narcissism

Question

A Narcissistic Number is a number which is the sum of its own digits, each raised to the power of the number of digits.

For example, take 153 (3 digits):

1³ + 5³ + 3³ = 1 + 125 + 27 = 153

1634:

1⁴ + 6⁴ + 3⁴ + 4⁴ = 1 + 1296 + 81 + 256 = 1634

The Challenge:

Your code must take input from the user and output True or False depending upon whether the given number is a Narcissistic Number.

Error checking for text strings or other invalid inputs is not required. 1 or 0 for the output is acceptable. Code that simply generates a list of Narcissistic Numbers, or checks the user input against a list, does not qualify.

OEIS A005188

Answer 1

APL (15)

∆≡⍕+/(⍎¨∆)*⍴∆←⍞

Outputs 1 if true and 0 if false.

Explanation:

• ∆←⍞: read a line (as characters), store in ∆
• (⍎¨∆)*⍴∆: evaluate each character in ∆ and raise it to the power ⍴∆
• ∆≡⍕+/: see if the input equals the string representation of the sum of these

Answer 2

GolfScript, 16 characters

~.`:s{48-s,?-}/!

Input must be given on STDIN, output is 0 or 1 indicating non-narcissistic / narcissistic number.

Explanation of the code:

~              # Evaluate the input to get a number
.              # Accumulator (initially the number itself)
`:s            # Convert number to string and assign to variable s
{              # Loop over characters of the string
  48-          # Reduce character value by 48
  s,           # Push length of input number
  ?            # Power
  -            # Subtract result from accumulator
}/
!              # Not! (i.e. iff accumulator was zero it was a narcissistic number)

Answer 3

Mathematica, 43 chars

Tr[#^Length@#&@IntegerDigits@#]==#&@Input[]

Answer 4

Perl, 38 characters

perl -lpe '$@=y///c;$s+=$_**$@for/./g;$_=$_==$s'

A pretty straightforward implementation.

Here's a slightly different version that fits in 35 characters:

perl -lpe '$@=y///c;$s+=$_**$@for/./g;$_-=$s'

This version outputs a false value if the input is narcissistic, otherwise it outputs a (Perl-accepted) true value. One might argue that this backwards version falls within the limits of the challenge description, but upon reflection I decided not to. I'm not that desperate to improve my score. Yet.

Answer 5

J, 23 chars

(".=+/@("."0^#))(1!:1)1

(1!:1)1 is keyboard input (returning a string).

". converts input to a number; "0 specifies a rank (dimension) of 0, in other words, taking each character and converting it to a number.

^ is the power function and # is the length function, thus taking each digit to the power of the length of the string (equivalently, the number of digits).

+/ is just sum, and = is comparing the sum and number.

Answer 6

Ruby, 34+5=39

With command-line flags

ruby -nlaF|

Run

p eval [$F,0]*"**#{~/$/}+"+"==#$_"

Outputs true or false.

Answer 7

R, 71 69 66 56 48

Reduced by 8 bytes thanks to @Giuseppe! The idea was to perform the integer division before the modulo operation.

i=nchar(a<-scan()):0;a==sum((a%/%10^i%%10)^i[1])

(3-year) old version with corresponding explanation:

i=nchar(a<-scan()):1;a==sum(((a%%10^i)%/%10^(i-1))^i[1])

a<-scan() takes a number (integer, real,...) as input (say 153 for the example).
i becomes a vector containing 3 to 1 (the number of characters of a being 3).
%% is vectorized so a%%10^i means a modulo 1000, 100 and 10: it therefore gives 153, 53, 3.
(a%%10^i)%/%10^(i-1) is the integer division of that vector by 100, 10, 1: therefore, 1, 5, 3.
We elevate that with the first element of i which is the number of characters (here digits) of a, i. e. 3, thus giving a vector containing 1, 125, 27 that we sum and compares to a.

Answer 8

Python 3, 56 bytes

Not very obfuscated, but a simple solution.

s = input()
print(int(s)==sum(int(c)**len(s)for c in s))

Answer 9

PHP, 80 74 66 chars

Very straightforward PHP solution:

<?for(;$i<$l=strlen($a=$argv[1]);)$s+=pow($a[$i++],$l);echo$s==$a;

It assumes error_reporting doesn't include notices, otherwise quite a few extra characters will be needed to initialize $s=0; and $i=0.

Thx @manatwork for shortening many chars.

Answer 10

K, 24 23

{x=+/xexp["I"$'a]@#a:$x}

Shaved 1 char with reordering

{x=+/{x xexp#x}"I"$'$x}

Answer 11

Dc: 48 characters

[1pq]Sr?d0rdZSz[d10/r10%lz^rSh+Lhd0!=c]dScx+=r0p

Sample run:

bash-4.1$ dc -e '[1pq]Sr?d0rdZSz[d10/r10%lz^rSh+Lhd0!=c]dScx+=r0p' <<< '153'
1

bash-4.1$ dc -e '[1pq]Sr?d0rdZSz[d10/r10%lz^rSh+Lhd0!=c]dScx+=r0p' <<< '1634'
1

bash-4.1$ dc -e '[1pq]Sr?d0rdZSz[d10/r10%lz^rSh+Lhd0!=c]dScx+=r0p' <<< '2013'
0

Answer 12

R, 53 bytes

sum(scan(t=gsub("(.)","\\1 ",x<-scan()))^nchar(x))==x

The gsub regex inserts spaces in between characters, so that the scan function will be able to read the number into a vector of digits.

Answer 13

Kona, 18

...

{x=+/(0$'u)^#u:$x}

Answer 14

Powershell, 75 63 62 60 58

Edit: Updated per @Iszi's comment (note: this counts on $x not existing)

Edit: Added @Danko's changes.

[char[]]($x=$n=read-host)|%{$x-="$_*"*$n.length+1|iex};!$x

58 56 chars

If input is limited to 10 digits (includes all int32)

($x=$n=read-host)[0..9]|%{$x-="$_*"*$n.length+1|iex};!$x

Answer 15

Python 2.x - 51

Same concept as crazedgremlin's solution for Python 3.x:

s=input();print s==sum(int(c)**len(`s`)for c in`s`)

Answer 16

C - 97 93 characters

a,b;main(c){scanf("%d",&c);b=c;for(;c;c/=10)a+=pow(c%10,(int)log10(b)+1);printf("%d",a==b);}

With indentation:

a,b;
main(c) { 
  scanf("%d",&c);
  b=c;
  for(;c;c/=10)
    a+=pow(c%10,(int)log10(b)+1);
  printf("%d",a==b);
}

Answer 17

Delphi - 166

uses System.SysUtils,math;var i,r,l:integer;s:string;begin r:=0;readln(s);l:=length(s);for I:=1to l do r:=round(r+power(strtoint(s[i]),l));writeln(inttostr(r)=s);end.

With indent

uses System.SysUtils,math;
var
  i,r,l:integer;
  s:string;
begin
  r:=0;
  readln(s);
  l:=length(s);
  for I:=1to l do
    r:=round(r+power(strtoint(s[i]),l));
  writeln(inttostr(r)=s);
end.

Answer 18

05AB1E, 7 bytes (Non-competing)

DSDgmOQ

Try it online!

-2 bytes thanks to @daHugLenny

Answer 19

Japt, 14 9 7 bytes

¶ì_xpZÊ

Try it online

---

Explanation

Implicit input of integer U.

ì_

Convert U to an array of digits (ì), pass it through a function and convert back to an integer after.

xpZÊ

Reduce by addition (x), raising each element to the power (p) of the length (Ê) of the array in the process.

¶

Check if the result is strictly equal to U.

Answer 20

Haskell 2010 - 76 characters

main=do x<-getLine;print$(==x)$show$sum$map((^length x).(+(-48)).fromEnum)x

Answer 21

Bash, 64 chars

for((a=$1;a>0;s+=(a%10)**${#1},a/=10));do :; done;echo $[s==$1]

a=$1;p=${#a};for((;a>0;a/=10));do s=$((s+(a%10)**p));done;echo $((s==$1))

Answer 22

Awk: 40 39 characters

{for(;i<NF;)s+=$(i+++1)**NF;$0=$0==s}1

Sample run:

bash-4.1$ awk -F '' '{for(;i<NF;)s+=$(i+++1)**NF;$0=$0==s}1' <<< '153'
1

bash-4.1$ awk -F '' '{for(;i<NF;)s+=$(i+++1)**NF;$0=$0==s}1' <<< '1634'
1

bash-4.1$ awk -F '' '{for(;i<NF;)s+=$(i+++1)**NF;$0=$0==s}1' <<< '2013'
0

Answer 23

JavaScript - 70 58 characters

for(i in a=b=prompt())b-=Math.pow(a[i],a.length)
alert(!b)

Note:

If you're testing this in your dev console on Stack Exchange, be aware that there are a number of non-standard properties added to String.prototype that will break this solution, such as String.prototype.formatUnicorn. Please be sure to test in a clean environment, such as on about:blank.

Answer 24

Lua (101 chars)

Lua isn't known for being concise, but it was fun to try anyway.

for n in io.lines()do l,s=n:len(),0 for i=1,l do d=n:byte(i)s=s+(d-48)^l end print(s==tonumber(n))end

Improvements welcome.

Answer 25

Java - 84 bytes

(a,l)->{int s=0;for(byte c:a.getBytes())s+=Math.pow(c-48,l);return a.equals(""+s);};

Non-lambda version: 101 bytes:

boolean n(String a,int l){int s=0;for(byte c:a.getBytes())s+=Math.pow(c-48,l);return a.equals(""+s);}

Called like this:

interface X {
    boolean n(String a, int l);
}

static X x = (a,l)->{int s=0;for(byte c:a.getBytes())s+=Math.pow(c-48,l);return a.equals(""+s);};

public static void main(String[] args) {
    System.out.println(n("153",3));
    System.out.println(n("1634",4));
    System.out.println(n("123",3));
    System.out.println(n("654",3));
}

Returns:

true
true
false
false

Answer 26

Jelly, 6 bytes (non-competing)

D*L$S=

Try it online!

D        Get the digits of the input
 *L$     Raise each element to power of its length
    S    Sum
     =   Equals input?

Answer 27

F# - 92 chars

let n=stdin.ReadLine()
n|>Seq.map(fun x->pown(int x-48)n.Length)|>Seq.sum=int n|>printf"%b"

Answer 28

Common Lisp - 116 102 characters

(defun f(m)(labels((l(n)(if(> n 0)(+(expt(mod n 10)(ceiling(log m 10)))(l(floor n 10)))0)))(= m(l m))))

Formatted:

(defun f(m)
  (labels((l(n)
            (if(> n 0)
               (+(expt(mod n 10)(ceiling(log m 10)))
                 (l(floor n 10)))
               0)))
    (=(l m)m)))

Answer 29

Smalltalk - 102 99 characters

[:n|a:=n asString collect:[:e|e digitValue]as:Array.^n=(a collect:[:each|each raisedTo:a size])sum]

At the Workspace, send value: with the number, and Print It.

Answer 30

APL (Dyalog Unicode), 8 bytes^SBCS

Tacit prefix function taking the input as a string.

⍎≡1⊥⍎¨*≢

Try it online!

⍎ is the evaluated argument

≡ identical to

1⊥ the sum (lit. convert from base-1) of

⍎¨ the evaluated characters (i.e the digits)

* raised to the power of

≢ the tally of characters (i.e. digits)

Answer 31

C#, 117

using System.Linq;class A{int Main(string[] a){return a[0].Select(c=>c-'0'^a[0].Length).Sum()==int.Parse(a[0])?1:0;}}

Answer 32

Retina, 118 bytes

Byte count assumes ISO 8859-1 encoding.

.*
$0 $0¶$0
(?<=^\d*)\d
x
(?=.*$)
¶
0¶

\d+
$*
¶(1+)
¶$1 $1
{`^x ?

}s`(?<=x.*)1(?=1* (1+))
$1
 1*

1¶1
11
^(1*)¶+\1\b

Try it online

---

Explanation

.*                          # Copy number 3 times. For Length, Unary, and Digits
$0 $0¶$0
(?<=^\d*)\d                 # Convert first copy to x's (Length)
x
(?=.*$)                     # Split up digits of last copy, each on their own line
¶
0¶                          # Remove zeros, because they leave blank lines

\d+                         # Convert to unary
$*
¶(1+)                       # Duplicate each separated digit
¶$1 $1
{`^x ?                      # While x's exist, remove an x ...

}s`(?<=x.*)1(?=1* (1+))     #     and multiply each value by the digit (nth power)
$1
 1*                         # Remove original digits

1¶1                         # Remove lines between digits
11
^(1*)¶+\1\b                 # Match if values are equal

Answer 33

Haskell, 68 66 bytes

d 0=[]
d n=mod n 10:d(div n 10)
sum.(\a->map(^length a)a).d>>=(==)

Usage:

*Main> sum.(\a->map(^length a)a).d>>=(==) $ 1634
True

Answer 34

Clojure, 85 bytes

#(= n(int(reduce +(vec(map#(Math/pow(Character/digit % 10)(count(str n)))(str n))))))

Usage is like so:

(#(...) {number})

Ungolfed (with commentary):

(defn narcissistic [n]
  ; The function is altered a bit, to improve readability.
  ; The double arrow means that a result of a function will get "chained"
  ; onto the next function as the last argument:
  ; (->> 1 (* 2) (+ 3)) -> (->> (* 2 1) (+ 3)) -> (+ 3 (* 2 1))
  (->> n
    ; Converts it to a string, for the next function
    ; 153 -> "153"
    str
    ; Converts the string to an array of characters,
    ; which is then raised to the powers equal to the length of the number:
    ; 153 -> (1.0 125.0 27.0)
    (map (#(Math/pow (Character/digit % 10) (count (str n)))))
    ; Converts the array to a vector (reducing only works with vectors)
    ; (1.0 125.0 27.0) -> [1.0 125.0 27.0]
    vec
    ; Reduces the vector by adding them
    ; [1.0 125.0 27.0] -> 153.0
    (reduce +)
    ; Turns that into an integer
    ; 153.0 -> 153
    int
    ; Checks if that's equal to the original n
    ; 153 = 153 -> true
    (= n)))

Answer 35

Befunge 98, 58 bytes

1-00p&:a\v
 00g1+00p>:a%\a/:!kv
 \:9`kv00gk:00gk*+>
@.!-$<

Try it Online!

I'm sure this can be golfed further. I will take another look at it and add an explanation later...

Answer 36

Add++, 16 bytes

L,BDdbLdXBcB`sA=

Try it online!

Answer 37

K (ngn/k), 22 bytes

{x~+/*/'(#:r)#'r:10\x}

Try it online!

Answer 38

Brachylog, 10 bytes

lg;?↔z^ᵐ+?

Try it online!

The predicate succeeds if the input is an Armstrong number and fails if it is not. If run as a full program, success prints true. and failure prints false.

lg;?↔z     A list of pairs [a digit of input, the length of input].
      ^ᵐ   A list of numbers where each is a digit of the input raised to the power of its length.
        +  The sum of those numbers.
         ? Attempt to unify that sum with the input.

Answer 39

Not the sortest but my take.

Python 2.7: 59 60 chars

a=input();(0,1)[sum(int(i)**len(str(a))for i in str(a))==a]

Answer 40

Pyth, 13 characters

JwqvJsm^vdlJJ

Explanation:

Jw                J=input()
       ^vdlJ      eval(d)^len(J)
      m^vdlJJ     map each character in J to eval(d)^len(J)
  qvJsm^vdlJJ     print(eval(J)==sum(map each character in J to eval(d)^len(J)))

Answer 41

Python, 90 Bytes

a,z=input(),[]
for x in list(a):z.append(int(x)**len(a))
print(1 if sum(z)==int(a) else 0)

Answer 42

C, 252 220 225 111 bytes

int f(char *a){for(int i=0;i<strlen(a);i++){r+=((int)a[i]);for(int j=0;j<strlen(a);j++)r*=r;}return r==(int)a;}

Returns 0 if false and 1 if true. Thanks to @DrMcMoylex for saving many bytes and explaining stuff.

Answer 43

JavaScript, 56 characters

n=prompt();n.split('').reduce((a,i)=>a+i**n.length,0)==n

This makes use of the exponentiation operator, so you have to be running a modern browser for this to work.

Answer 44

Perl, 27 +3 = 30 bytes

Run with -F. Older versions of Perl might require you to run with -nF instead, if -F does not imply -n.

grep$;+=$_**$#F,@F;say$_==$

Prints 1 if narcissistic, prints nothing otherwise.

(thanks to @Dada for byte-count correction, and for -2 bytes)

Answer 45

Pyke, 8 bytes (noncompeting)

YQ`lL^sq

Try it here!

 Q`l     -   len(str(input))
    L^   -  map(^ ** V)
Y        -   digits(input)
      s  -  sum(^)
       q - ^ == input

Answer 46

JavaScript (ES6), 56 bytes

eval(`${n=prompt()}0`.split``.join(`**${n.length}+`))==n

Answer 47

Pushy, 9 bytes

Note that this answer is non-competing as Pushy postdates the challenge. However, I thought I'd post it because it's interestingly short for a simple stack-based language:

VsLKeS^=#

Try it online!

It works like this (how the two stacks would look for the example input is shown on the right):

    \ Implicit input, for example 1634.  [1634], []
V   \ Copy into second stack.            [1634], [1634]
s   \ Split into individual digits       [1,6,3,4], [1634]
L   \ Push stack length                  [1,6,3,4,4], [1634]
Ke  \ Raise all to this power            [1,1296,81,256], [1634]
S   \ Take sum                           [..., 1634], [1634]
^=  \ Check equality with initial input  [..., True], []
#   \ Output this boolean (as 0/1)     

Answer 48

Perl 6, 30 bytes

{$_==sum .comb.map(* **.comb)}

Pretty straightforward. The chars method would be more typically used to get the number of characters in the input string, but comb returns those characters as a list, which evaluates to the number of characters in numeric context, and saves us a byte.

Answer 49

JavaScript (ES7), 43 38 bytes

Takes input as a string.

n=>n==eval([...n,0].join`**n.length+`)

---

Try It

f=
n=>n==eval([...n,0].join`**n.length+`)
o.innerText=f(i.value="153")
oninput=_=>o.innerText=f(i.value)

<input id=i type=number><pre id=o>

Answer 50

Bash, 54 bytes

echo $[ `printf "+%c**${#1}" $(fold -w1<<<$1)` == $1 ]

Try it online!

Takes input as parameter, outputs 1 if is narcissist, 0 if not.

fold prints each digit one per line, printf adds +<digit>**<length> forming the arithmetic expression which is evaluated and compared to the original input.

Answer 51

Python 2, 44 bytes

I think this is the shortest you can get for Python. Uses a lambda rather than a full program.

lambda s:sum(int(x)**len(`s`)for x in`s`)==s

Try it online!

Based off @danmcardle's answer.

Original answer, 51 bytes

lambda s:sum(map(lambda x:int(x)**len(`s`),`s`))==s

Try it online!

Answer 52

Pyth (non-competing), 10 bytes

qsm^sdl`Q`

Verify the test cases.

Answer 53

Perl 5, 24 bytes

21 bytes of code + 3 for -pF flags

for$i(@F){$_-=$i**@F}

Try it online!

Answer 54

Swift 3.2: 107 characters

Of course Swift is absolutely not a quick language but I thought I would try:

func n(s:String){let c=s.utf8.map{Double($0)-48};print(c.reduce(0){$0+pow($1,Double(c.count))}==Double(s))}

Answer 55

JavaScript 46 bytes

F=n=>![...n].reduce((x,c)=>x-(+c)**n.length,n)

console.log(F("153") == true)
console.log(F("370") == true)
console.log(F("371") == true)
console.log(F("152") == false)
console.log(F("150") == false)

Answer 56

Pyt, 11 bytes

ĐĐḶ⌊⁺⇹ą⇹^Ʃ=

Explanation:

                      Implicit input
ĐĐ                    Duplicate the input twice
   Ḷ⌊⁺                Get number of digits in the input
      ⇹ą              Convert input to array of digits
        ⇹^Ʃ           sum the digits raised to the power of the number of digits
           =          equals input?

Try it online!

Answer 57

JavaScript 7, 41 Bytes

s=>[...s].map(x=>N+=x**s.length,N=0)|N==s

Answer 58

CJam, 12 bytes

{_Ab_,f#:+=}

Try it online!

Explanation:

{          }   anonymous block, input: 1634
   b           get digits in base
  A              10: [1 6 3 4]
     ,         take the length: 4
       #       and raise
      f          each element
    _              of the list of digits
               to that power: [1 1296 81 256]
        :      fold over
         +       addition: 1634
          =    and compare
 _               to the original: 1 (true)

Answer 59

Kotlin, 60 bytes

map{Math.pow(it-'0'+0.0,length+0.0)}.sum()==this.toInt()+0.0

Beautified

map {
    Math.pow(it - '0' + 0.0, length + 0.0)
}.sum() == this.toInt() + 0.0

Test

fun String.f() =
map{Math.pow(it-'0'+0.0,length+0.0)}.sum()==this.toInt()+0.0

fun main(args: Array<String>) {
    (0..1000).filter { it.toString().f() }.forEach { println(it) }
}

TIO

TryItOnline

Answer 60

Javascript (ES6) 46 bytes - Not competing

n=>(s=[...''+n]).forEach(v=>n-=v**s.length)|!n

Explanation:

n=>
(s=[...''+n])        // Convert input to array of chars and assign to s
  .forEach(v=>       // Loop over s (returns undefined)
    n-=v**s.length)  // reduce input by char^length
  |                  // undefined is falsy, so we OR
  !n                 // OR with negated input 
                     // returns 1 if 0, 0 otherwise

Answer 61

R - 216

Here is a long-ish R attempt:

fnNar = function(x = NULL) {
  if(is.null(x)) x = readline('Enter a positive integer: ')
  digits = as.double(unlist(strsplit(as.character(x), split = '')))
  exponent = length(digits)
  return(x == sum(digits ^ exponent))
}

# test the function
fnNar()

# test the function
fnNar(153)
fnNar(1634)
fnNar(101)

Answer 62

Pari/GP, 35 bytes

n->n==vecsum([d^#s|d<-s=digits(n)])

Try it online!

Answer 63

Ly, 51 bytes

ns>lS0sp11[ppl:Isp>l<ysp>l<sp>,^<l`sy,=!]>&+s<<l=fp

Try it online!

Answer 64

Tcl, 77 bytes

proc N n {expr [join [lmap d [split $n ""] {expr $d**[string le $n]}] +]==$n}

Try it online!

Answer 65

Python 2.7 - 57 chars

i=`input()`
print`sum(map(lambda x:int(x)**len(i),i))`==i

There is a shorter Python answer, but I might as well toss in my contribution.

i=`input()`

i is set to input() surrounded by backticks (which is surprisingly hard to type through SE's markdown interpreter). Surrounding x with backticks is equivalent to str(x). [backtick]input()[backtick] saves two characters over raw_input() in any case where we can assume the input is an int, which we're allowed to do:

Error checking for text strings or other invalid inputs is not required.

Once i is a string containing the user's input, the next line is run. I'll explain this one from the inside out:

map(lambda x:int(x)**len(i),i)

map is a function in Python that takes a function and an iterable as arguments and returns a list of each item in the iterable after having the function applied to it. Here I'm defining an anonymous function lambda x which converts x to a string and raises it to the power of the length of i. This map will return a list of each character in the string i raised to the correct power, and even nicely converts it to an int for us.

`sum(map(lambda x:int(x)**len(i),i))`

Here I take the sum of each value in the list returned from the map. If this sum is equal to the original input, we have a narcissistic number. To check this, we either have to convert this sum to a string or the input to an int. int() is two more characters than two backticks, so we convert this to a string the same way we did with the input.

print`sum(map(lambda x:int(x)**len(i),i))`==i

Compare it to i and print the result, and we're done.

Answer 66

Racket 115 bytes

(let*((l(number->string n))(g(string-length l))(m(for/sum((i l))(expt(string->number(string i))g))))(if(= m n)1 0))

Ungolfed:

(define (f n)
  (let* ((l (number->string n))
         (g (string-length l))
         (m (for/sum ((i l))
              (expt (string->number(string i)) g))))
    (if (= m n) 1 0)))

Testing:

(f 153)
(f 1634)
(f 123)
(f 654)

Output:

1
1
0
0

Answer 67

Jelly, 7 bytes (non-competing)

D*DL$S⁼

Try it online!

Or alternatively (uses 2 chains):

Dµ*LS⁼Ḍ

Explanation of the first code:

 D* DL$S⁼  Main link (monadic). Arguments: z
⁸          (implicit) z
 D         List of digits of z
   ⁸       (implicit) z
    D      List of digits of z
     L     Length of z
      $    Last two links as a monad
  *        Exponentiation with base x and exponent y
       S   Sum of z
         ⁸ (implicit) z
        ⁼  Check if x equals y

Answer 68

C#, 103 Bytes

Golfed:

bool N(int n){double a=0;foreach(var d in n+""){a+=Math.Pow(int.Parse(d+""),n+"".Length);}return a==n;}

Ungolfed:

public bool N(int n)
{
  double a = 0;

  foreach (var digit in n.ToString())
  {
    a += Math.Pow(int.Parse(digit + ""), n.ToString().Length);
  }

  return a == n;
}

Testing:

Console.WriteLine(new NarcissisticNumber().N(153));
True

Console.WriteLine(new NarcissisticNumber().N(1634));
True

Answer 69

Clojure, 110 bytes

(fn[](let[s(read-line)p #(Integer/parseInt(str %))](=(p s)(reduce + 0(map #(int(Math/pow(p %)(count s)))s)))))

Reads in the user input, maps over the digits, raising each to a power equal to the number of digits in the number, then checks that the sum of the digits equals the number itself.

Ungolfed (and neatened up):

(defn narcissistic? []
  (let [n-str (read-line)
        parse #(Integer/parseInt (str %))
        pow #(int (Math/pow % (count n-str)))
        powd-digits (map #(pow (parse %)) n-str)]
    (= (parse n-str) (reduce + 0 powd-digits))))

Answer 70

JavaScript ES6, 50 bytes

v=>[...s=v+""].map(x=>v-=Math.pow(x,s.length))&&!v

Convert the number to a string and iterate through the digits, subtract the power computation from the original number use the ! operator to invert the logic so that a 0 result returns true and non-zero returns false.

Answer 71

k, 24 bytes

{x=+/*/(#$x)#,"I"$'$x}

Answer 72

R, 173 Bytes

a=readline()
b=as.numeric(strsplit(as.character(a),"")[[1]])
x=(b)^length(b)
if(sum(x)==as.numeric(paste(b,sep="",collapse=""))){
   print("true")
} else{
  print("false")
}

Answer 73

Factor, 90 bytes

[ read [ length ] [ >array [ 1string ] map [ 10 base> ] map ] bi [ swap ^ ] with map sum ]

More readable and explained:

[ 
    read                                  ! input 
    [ length ]                            ! a function which gets the length 
    [ >array [ 1string ] map [ 10 base> ] map ] ! another which turns a number into an array
    bi                                    ! apply both to the string input
    [ swap ^ ] with map sum               ! raise each digit to the length power and sum
]