It is 1 which appears to be a prime number however it's neither a prime number or a composite number since it has just a single factor which is itself.
A prime number is a whole number greater than 1 whose just factors are 1 and itself. A factor is a whole numbers that can be partitioned evenly into another number. The initial couple of prime numbers are 2, 3, 5, 7, 11, 13, 17, 19, 23 and 29.