No.
When you are finding common factors, one method is to list the factors.
The factors of 21 are 1, 3, 7, and 21 which means that 21 is composite.
2,3,4,6,8,9,12,18,24,36 are all the factors.
List them all, and multiply to see if you get the original number.
The list of composite numbers is infinite.
That's an infinite list.
When a composite number is expressed as a product of its prime factors, the prime factorization of the composite number has been performed.
The list of composite numbers is infinite. They all have more than two factors.
You do! You first list all the factors of a number. A prime number has only 2 factors which are 1 and itself. Composite numbers are everything else except 1 and 0. 1 and 0 are neither prime, nor composite.
composite 1, 3, 9
That's an infinite list.