181 (number)

181 (one hundred [and] eighty-one) is the natural number following 180 and preceding 182.

← 180 181 182 →
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Cardinal	one hundred eighty-one
Ordinal	181st (one hundred eighty-first)
Factorization	prime
Prime	42nd
Divisors	1, 181
Greek numeral	ΡΠΑ´
Roman numeral	CLXXXI
Binary	101101012
Ternary	202013
Quaternary	23114
Quinary	12115
Senary	5016
Octal	2658
Duodecimal	13112
Hexadecimal	B516
Vigesimal	9120
Base 36	5136

In mathematics

• 181 is an odd number
• 181 is a centered number
  • 181 is a centered pentagonal number[1]
  • 181 is a centered 12-gonal number[2]
  • 181 is a centered 18-gonal number[3]
  • 181 is a centered 30-gonal number
  • 181 is a centered square number[4]
  • 181 is a star number that represents a centered hexagram (as in the game of Chinese checkers)
• 181 is a deficient number, as 1 is less than 181
• 181 is an odious number
• 181 is a prime number
  • 181 is a Chen prime[5]
  • 181 is a dihedral prime
  • 181 is a full reptend prime[6]
  • 181 is a palindromic prime
  • 181 is a strobogrammatic prime, the same when viewed upside down
  • 181 is a twin prime with 179
• 181 is a square-free number
• 181 is an undulating number, if written in the ternary, the negaternary, or the nonary numeral systems
• 181 is the difference of 2 square numbers: 91² – 90²
• 181 is the sum of 2 consecutive square numbers: 9² + 10²
• 181 is the sum of 5 consecutive prime numbers: 29 + 31 + 37 + 41 + 43

In geography

• Langenburg No. 181, Saskatchewan rural municipality in Saskatchewan, Canada
• 181 Fremont Street proposed skyscraper in San Francisco, California
• 181 West Madison Street, Chicago

In the military

• 181st (Brandon) Battalion, CEF was a unit in the Canadian Expeditionary Force during World War I
• 181st Airlift Squadron is a unit of the Texas Air National Guard
• 181st Infantry Brigade of the United States Army based at Fort McCoy, Wisconsin
• 181st Intelligence Wing is a unit of the United States Air Force located at Hulman Field, Terre Haute, Indiana
• AN/APQ-181 an all-weather, low probability of intercept (LPI) radar system for the U.S. Air Force B-2A Spirit bomber aircraft
• Bücker Bü 181 Bestmann single-engine trainer aircraft during World War II
• USNS Adelphi (T-AG-181) was a ship scheduled to be acquired by the United States Navy, however, the program was cancelled
• USNS Fred C. Ainsworth (T-AP-181) was a United States Navy troop transport during World War II
• USNS Potomac (T-AO-181) was a United States Navy oiler following the Vietnam War
• USS Accokeek (ATA-181) was a United States Navy ATA-174-class auxiliary ocean tugboat during World War II
• USS Flagler (AK-181) was a United States Navy Alamosa-class cargo ship following World War II
• USS Hopewell (DD-181) was a United States Navy Wickes-class destroyer following World War I
• USS Pompano (SS-181) was a United States Navy Porpoise-class submarine during World War II
• USS Straub (DE-181) was a United States Navy Cannon-class destroyer escort during World War II

In movies

• “181: Fragments of a Journey in Palestine-Israel,” winner of the 2005 Yamagata International Documentary Film Festival
• The war film “The Enemy Below” revolves around the fictitious Buckley-class destroyer escort, USS Hayes (DE-181) and a German U-boat

In transportation

• The Volkswagen 181
• Lufthansa Flight 181, which was hijacked on October 13, 1977
• London Buses route 181
• 181 Union City-New York, a New Jersey Transit bus route from New Jersey to New York
• The Córas Iompair Éireann CIE 181 Class diesel locomotives, and numbered B181 to B192, built by General Motors Electro-Motive Division (EMD) in 1966
• East 181st Avenue, a light rail station on the MAX Blue Line in Gresham, Oregon
• New York City Subway stations in Manhattan:
  • 181st Street (IND Eighth Avenue Line), at Fort Washington Avenue served by the A train
  • 181st Street (IRT Broadway – Seventh Avenue Line), at St. Nicholas Avenue served by the 1 train
• 181st Street (Manhattan)
• Oregon Route 229, also known as the Siletz Highway No. 181

In other fields

181 is also:

• The year AD 181 or 181 BC
• The atomic number of an element temporarily called Unoctunium
• 181 Eucharis is a large K-type Main belt asteroid
• Minuscule 181 (in the Gregory-Aland numbering), α 101 (Soden), is a Greek minuscule manuscript of the New Testament
• Mir-181 microRNA precursor is a small non-coding RNA molecule
• The number of channels on an older American television set, with 68 over-the-air television channels (12 VHF channels [2 through 13] and 56 UHF channels [14 through 69]) and 113 cable television channels (channel 1 and channels 14 through 125, excluding VHF channels 2 through 13)

See also

• List of highways numbered 181
• United Nations Security Council Resolution 181
• United Nations General Assembly Resolution 181 (II) Future Government of Palestine
• United States Supreme Court cases, Volume 181
• Pennsylvania House of Representatives, District 181
• Criminal Code of Belarus, Article 181
• Constitution of Malaysia, Article 181

References

1. "Sloane's A005891 : Centered pentagonal numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-26.
2. "Sloane's A003154 : Centered 12-gonal numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-26.
3. "Sloane's A069131 : Centered 18-gonal numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-26.
4. "Sloane's A001844 : Centered square numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-26.
5. "Sloane's A109611 : Chen primes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-26.
6. "Sloane's A001913 : Full reptend primes". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-26.

External links

• Number Facts and Trivia: 181
• The Number 181
• The Positive Integer 181
• Prime curiosities: 181
• VirtueScience: 181
• Number Gossip: 181
• 181 FM Internet radio