When a number is multiplied by itself, it is a square number. A perfect square number is the square of a natural number, such as 225 being the square of 15. The square root of a number is found by dividing the number by its own square. Pythagorean triplets are sets of three natural numbers where the sum of the squares of the first two equals the square of the third, like 3, 4, 5. Perfect square numbers always have an even number of zeros at the end.