1 is neither prime nor composite, so what should we called it ?
The number 1 is a unit - "unity" - it is neither prime nor composite.
It is a matter of definition. It looks as if 1 should be a prime because 1 is only divisible by 1 and itself, but a prime is defined to be a number with exactly two factors - 1 and itself - but 1 has only one factor.
In addition, stated positively then, the number 1 is the first, non-zero, natural number.
Number one has a unique role as the identity element of multiplication. You might call it that.
At one time, 1 was viewed as a prime number, but this can cause problems.