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**50** (**fifty**) is the natural number following 49 and preceding 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 | 110010_{2} | |||

Ternary | 1212_{3} | |||

Octal | 62_{8} | |||

Duodecimal | 42_{12} | |||

Hexadecimal | 32_{16} |

**Fifty** is the smallest number that is the sum of two non-zero square numbers in two distinct ways: 50 = 1^{2} + 7^{2} = 5^{2} + 5^{2}.^{[1]} It is also the sum of three squares, 50 = 3^{2} + 4^{2} + 5^{2}, and the sum of four squares, 50 = 6^{2} + 3^{2} + 2^{2} + 1^{2}. It is a Harshad number.^{[2]}

50 is a Stirling number of the first kind: , and also a Narayana number:

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]}

Look up **fifty** in Wiktionary, the free dictionary.

- The atomic number of tin
- The fifth magic number in nuclear physics

- In Kabbalah, there are 50 Gates of Wisdom (or Understanding) and 50 Gates of Impurity
^{[citation needed]} - The traditional number of years in a jubilee period.
^{[5]} - The Christian Feast of Pentecost takes place on the 50th day of the Easter Season
- The Jewish Pentecost takes place 50 days after the Passover feast (the holiday of Shavuoth).

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

**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*^{[6]} - 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.

**^**de Koninck, J.M. (2009).*Those fascinating numbers*. AMS Bookstore. p. 18. ISBN 0-8218-4807-0.**^**"Sloane's A005349 : Niven (or Harshad) numbers".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-30.**^**"Sloane's A005277 : Nonients".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-30.**^**"Sloane's A005278 : Noncotients".*The On-Line Encyclopedia of Integer Sequences*. OEIS Foundation. Retrieved 2016-05-30.**^**Leviticus 25:10**^**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.