50 (number)

50 (fifty) is the natural number following 49 and preceding 51.

This article is about the number. For the year, see AD 50. For other uses, see 50 (disambiguation).

← 49 50 51 →
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Cardinal	fifty
Ordinal	50th (fiftieth)
Numeral system	quinquagesimal
Factorization	2 × 5^2
Divisors	1, 2, 5, 10, 25, 50
Greek numeral	Ν´
Roman numeral	L
Unicode symbol(s)	ↆ
Binary	1100102
Ternary	12123
Octal	628
Duodecimal	4212
Hexadecimal	3216

In mathematics

Fifty is the smallest number that is the sum of two non-zero square numbers in two distinct ways: 50 = 1² + 7² = 5² + 5².[1] It is also the sum of three squares, 50 = 3² + 4² + 5², and the sum of four squares, 50 = 6² + 3² + 2² + 1². It is a Harshad number.[2]

There is no solution to the equation φ(x) = 50, making 50 a nontotient.[3] Nor is there a solution to the equation x − φ(x) = 50, making 50 a noncototient.[4]

In science

• The atomic number of tin
• The fifth magic number in nuclear physics
• The percent of genetic overlap of a parent and offspring.[5]

In religion

• In Kabbalah, there are 50 Gates of Wisdom (or Understanding) and 50 Gates of Impurity
• The traditional number of years in a jubilee period.[6]
• The Christian Feast of Pentecost takes place on the 50th day of the Easter Season

In sports

• In cricket one day internationals, each side may bat for 50 overs.

In other fields

Fifty is:

• There are 50 states in the United States of America. The TV show Hawaii Five-O and its reimagined version, Hawaii Five-0, are so called because Hawaii is the last (50th) of the states to officially become a state.
• 5-O (Five-Oh) - Slang for police officers and/or a warning that police are approaching. Derived from the television show Hawaii Five-O[7]
• A calibre of ammunition (0.50 inches: see .50 BMG)
• In millimetres, the focal length of the normal lens in 35 mm photography
• The percentage (50%) equivalent to one half, so that the phrase "fifty-fifty" commonly expresses something divided equally in two; in business this is often denoted as being the ultimate in equal partnership
• In years of marriage, the gold or "golden" wedding anniversary
• The speed limit, in kilometres per hour, of Australian and Canadian roads with unspecified limits.

References

1. de Koninck, J.M. (2009). Those fascinating numbers. AMS Bookstore. p. 18. ISBN 0-8218-4807-0.
2. "Sloane's A005349 : Niven (or Harshad) numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
3. "Sloane's A005277 : Nonients". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
4. "Sloane's A005278 : Noncotients". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-30.
5. Adkison, Linda (2011). Elsevier's Integrated Review Genetics. p. 42.
6. Leviticus 25:10
7. Karen Rhodes (1 February 1997). Booking Hawaii Five-O: An Episode Guide and Critical History of the 1968–1980 Television Detective Series. McFarland. p. 265. ISBN 978-0-7864-8666-3.