It is the only even prime number
It is composite because it has more than two factors
75 is a composite number because it has more than 2 factors
56 is a composite number because it has more than 2 factors
31 is a prime number because it has only two factors which are itself and one
A prime number has only 2 factors which are 1 and itself. Composite numbers are everything else except 1 and 0. 1 and 0 are neither prime, nor composite. 5 is prime.
Forty three is a prime number because you cannot divide it evenly with another number. Composite numbers are numbers that can be divided evenly. For example, 40 and 42 are composite numbers.
The Number 7 is a prime number
There are lots of numbers which are neither. For example, pi, -7, 0, 1, sqrt(7).
7 is a prime number but 1 is neither prime nor composite.