To determine if 128 is a prime number or a composite number, we simply look at the factors for 128.
If the factors of 128 are only 128 and 1, then we know that 128 is a prime number. Otherwise, 128 is a composite number.
To explain better, if 128 is only divisible by 1 and 128, then it is a prime number, and if 128 is divisible by more than 128 and 1, then it is a composite number.
The factors of 128 are as follows:
1, 2, 4, 8, 16, 32, 64, 128
Therefore, since 128 is divisible by more than one and itself, the answer to the
question "Is 128 prime or composite?" is highlighted in blue below.
composite
Is 129 prime or composite?
OK. Now you know that 128 is a composite number. Use our logic above and see if
you can figure out if the next number on our list is prime or composite before you check your answer.

