Question

Why is 1 neither prime nor composite numbers?

Answer 1

Definition of prime number is that a positive number which has only 2 factors, ie 1 and the number itself other than 1 .

Definition of composite number is that a positive number which has atleast one positive factor other than 1 and the number itself.

As you can see, 1 doesn't satisfies the basic Definition of prime and composite number. Hence 1 is neither prime nor composite.