A perfect square is a positive integer that is obtained by multiplying an integer by itself. In other words, it is the product of some integer with itself. For example, 9 is a perfect square because it is the product of 3 by itself, 3 × 3 = 9. Similarly, 16 is a perfect square because it is the product of 4 by itself, 4 × 4 = 16. The following observations can be made to identify a perfect square:

• The numbers ending with 3 and 7 will have 9 as the units place digit in its square number.
• The number ending with 5 will have 5 as its units place digit in its square number.
• The number ending with 4 and 6 will have 6 as the units place digit in its square number.
• The number ending with 2 and 8 will have 4 as the units place digit in its square number.

To find a perfect square, we need to multiply the whole number by itself. The first 20 perfect square numbers are 1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225, 256, 289, 324, 361, and 400. Taking the square root of a perfect square always gives an integer.