1, 4, 9, 16, 25, 49, 64, ... Are called square numbers. They
are all equal to the product of a whole number with itself:

1 = 1 x 1, 4 = 2 x 2, 9 = 3 x 3, 16 = 4 x 4, 25 = 5 x 5,
36 = 6 x 6, 49 = 7 x 7, 64 = 8 x 8 etc.

Any number which can be expressed in this way is called a square
number.

For example 56169 is square as it is equal to 237 x 237. The
name square comes from the fact that a square number of dots can
be arranged in a square pattern.