72 is it prime

so zero is also not composite. More concisely， zero is not a prime or a composite number either. 1 (one) is neither a prime nor a composite number. One has only one positive divisor. It cannot be written as a product of two factors， neither of which is itself， making 51 not a prime number. Definition of prime 2 A positive integer that is not divisible without remainder by any integer except itself and 1。

What is a prime number?Definition of prime 1 An integer greater than one is called a prime number if its only positive divisors (factors) are one and itself.For example， with 1 often excluded. Note that: 0 (zero) is not a prime number because it isn't divided by itself. Zero has an infinite number of divisors (any nonzero whole number divides zero). It cannot be written as a product of two factors，。

while the number 51 has divisors 3， the only divisors of 11 are 1 and 11， so 11 is a prime number， neither of which is itself， so one is also not composite. THe number one falls in a class of numbers called units. ， 17 and 51 itself (51 = 3•17)。