A number (other than 1) which is not a prime number is called a composite number.
If a prime of the second form gets into your composite number, then that number cannot be the sum of two squares.
An integer that can be divided by at least one other integer besides itself and 1 without leaving a remainder. 24 is a composite number since it can be divided by 2, 3, 4, 6, 8, and 12. No prime numbers are composite numbers. Compare prime number.