composite.
It is composite.
Yes.
No, it is composite.
51 is composite.
54 is a composite number, not prime, because 2, 3, and 6 also go into it.
21 is not a prime number.
A composite number is made up of a product of prime numbers. It might be considered a non-prime number.
1 is not considered to be a prime or composite number because it has only one factor which is itself.
57 is a prime 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.
If a number has more than two factors then it is a composite number otherwise it is a prime number and 1 is not considered to be a composite or a prime number.
Well, yes, the number 1 is usually considered in a special category. It is not considered prime, but it isn't composite, either.