4 is a composite number. A prime number is a number greater than 1 that has no positive divisors other than 1 and itself. In contrast, a composite number has more than two positive divisors.
For example, the number 4 can be divided evenly by 1, 2, and 4. Since it has more than two divisors, it is classified as a composite number. Prime numbers, on the other hand, like 2, 3, 5, and 7, can only be divided evenly by 1 and themselves.
Understanding the difference between prime and composite numbers is fundamental in mathematics, especially in topics like number theory and cryptography.