You find all the factors of 51. The factors are 1, 51, 3, 17. A Prime number has only 2 factors which are 1 and itself. Composite numbers are everything else except 1, 2, and 0. 51 is COMPOSITE.
51 is composite.
51 composite, 61 prime.
composite
51 is composite.
prime
prime
It is composite.
51 is composite, 103 is prime.
Composite.
composite
It is composite.
51 is a composite number because 3 X 17 = 51 and 1 X 51 = 51.