To understand this problem, we must first know what a factor is.

The factor of the number "a" refers to an integer divisible by a. For example, the factor of 1 is only1; The factors of 2 are 1 and 2; The factor of 6 is 1, 2, 3, 6; The factors of 8 are 1, 2, 4, 8 and so on.

If a number has only two factors (1 and itself), it is called a prime number. For example, 2, 3, 5 and 7 are all prime numbers.

If a number has more than two factors, it is called a composite number. For example, 4, 6, 8, 9, 10 are all composite numbers.

1 is a special case. It is neither a prime number nor a composite number.