50 (fifty) is the natural number following 49 and preceding 51.
Fifty is the smallest number that is the sum of two non-zero square numbers in two distinct ways: 50 = 12 + 72 = 52 + 52. 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.
There is no solution to the equation φ(x) = 50, making 50 a nontotient. Nor is there a solution to the equation x − φ(x) = 50, making 50 a noncototient.
The atomic number of tin
The fifth magic number in nuclear physics
The percent of genetic overlap of a full sibling, a parent and offspring.
In Kabbalah, there are 50 Gates of Wisdom (or Understanding) and 50 Gates of Impurity
The traditional number of years in a jubilee period.
50 goals in 50 games is a milestone achievement in the NHL, first set by Maurice "Rocket" Richard in the 1944-45 season.
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
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
Nickname 50 Cent, a rapper.
A Canadian brand of beer called 50 Ale created in 1950 by Labatt breweries to commemorate 50 years of partnership. It is a popular brand still sold today.
The fiftieth pope was Pope Anastasius II.
The speed limit, in kilometres per hour, of Australian and Canadian roads with unspecified limits.
In the 1994 action movie Speed, which depicts a Los Angeles cop (Keanu Reeves), who must rescue civilians on a bus that has a bomb rigged to it which will detonate if the bus's speed drops below 50 mph.
