Which of these numbers is composite?

A composite number is defined as a positive integer that has at least one positive divisor other than one and itself. In other words, composite numbers can be divided evenly by numbers in addition to just one and the number itself.

The number 15 is composite because it can be divided by 1, 3, 5, and 15. This means it has factors besides just 1 and 15, satisfying the definition of a composite number. In contrast, the other options—13, 7, and 19—are all prime numbers. Prime numbers are defined as numbers greater than 1 that have no positive divisors other than 1 and themselves, meaning they cannot be divided evenly by any other numbers.

Thus, 15 stands out as the only composite number among the choices provided.