45 is a composite number.
A prime number is defined as a number greater than 1 that has no positive divisors other than 1 and itself. In contrast, a composite number has more than two distinct positive divisors. For the number 45, we can find its divisors: 1, 3, 5, 9, 15, and 45. Since it has divisors other than 1 and 45, it qualifies as a composite number. Additionally, 45 can be divided evenly by 3 and 5, which further confirms its composite status.