## Perfect Square

A natural number is called a perfect square if it is the square of a natural number. Perfect squares are also called square numbers.

For example, the numbers 1, 4, 9, 16, 25 are perfect squares because

1^{2}= 1 = 1 × 1

2^{2}= 4 = 2 × 2

3^{2}= 9 = 3 × 3

4^{2}= 16 = 4 × 4

5^{2}= 25 = 5 × 5

However, numbers such as 6 and 10 can not be written as square of natural numbers.

6 = 2 x 3 and 10 = 2 x 5