- The number of days in each of the 24 cycles of the Chinese calendar.
- The number of guns in a gun salute to Army, Marine Corps, and Air Force Lieutenant Generals, and Navy and Coast Guard Vice Admirals.
- The number of checkers each side has at the start of a backgammon game.
- The 15 puzzle.
- The number of balls in the eight ball variant of billiards
- The number of letters in the words “uncopyrightable”, “dermatoglyphics”, “misconjugatedly”, and “hydropneumatics”, which are the longest words in the English language that do not repeat a letter.
- The number of minutes in one quarter of an hour; 15 minutes past or before an hour is often known as quarter past and quarter to, respectively. (http://en.wikipedia.org/wiki/15_(number))