54

54 is the smallest number that can be written as the sum of 3 squares in 3 ways: 1² + 2² + 7² = 2² + 5² + 5² = 3² + 3² + 6² = 54.


The number of colored squares on a Rubik’s cube.

A polygonal number can be represented as nested points arranged in the form of a regular polygon. 54 is a nonadecagonal (19-gonal) number: 1, 19, 54, 106, 175, . . .

Sources: Wikipedia; Number Gossip