A square number (also known as a perfect square) is an integer that can be written as the product of an integer with itself. For example, 16 is a square number, since it can be written as 4 × 4 or 4².

The first 10 square numbers are: 1, 4, 9, 16, 25, 36, 49, 64, 81, 100

0 squared is a special case, 0 being the zeroth square.

Square numbers are always non-negative.