Fifteen (15, XV) is the natural number following fourteen and preceding sixteen. Fifteen is a triangular number. It is a composite number; its proper divisors being 1, 3 and 5. Its factorization is

In hexadecimal, as well as all higher bases, fifteen is represented as F. Fifteen is the magic result of a 3 by 3 magic square:

Fifteen is also:

  • The atomic number of phosphorous.
  • The number of guns in a gun salute to Army, Air Force and Marine Corps Lieutenant Generals, and Navy and Coast Guard Vice Admirals.
  • The designation of Interstate 15, a freeway that runs from California to Montana.
  • The age of a quinceañera, a Hispanic girl celebrating her fifteenth birthday.
  • The age for obtaining a driver's permit in jurisdictions where the age for a driver's license is sixteen.
  • The number of players on a rugby union team.

See also: thirteen, fourteen, fifteen, sixteen, seventeen, integer, list of numbers.

This article is about the number. For the year AD 15, see 15. For information on the television program, see Fifteen (TV show)