Why is 1 not prime??explain why

A prime number is a number with 2 factors. Since 1 has only 1 factor, it is not prime, because it doesn't have 2 factors.

A prime number is a number that has two factors that are itself and 1.
E.g 2 is a prime number because the two factors are 2 and 1.
E.g 3 is a prime number because the two factors are 3 and 1.

1 is taken as a natural benchmark for defining prime numbers. It is excluded from being a prime number.