California Assessment of Student Performance and Progress (CAASPP) Math Practice Exam

Which of the following is a prime number?

1. 15

2. 21

3. 29

4. 35

The correct answer is: 29

A prime number is defined as a natural number greater than 1 that has no positive divisors other than 1 and itself. To determine which number from the list is prime, we can analyze each option. The number 29 fits the definition of a prime number because it can only be divided evenly by 1 and 29. It has no other divisors, which confirms its status as prime. In contrast, the numbers 15, 21, and 35 have more than two positive divisors. For example, 15 can be divided by 1, 3, 5, and 15; 21 can be divided by 1, 3, 7, and 21; and 35 can be divided by 1, 5, 7, and 35. Since these numbers have divisors other than 1 and themselves, they do not meet the criteria for prime numbers. Thus, 29 stands out as the only prime number among the provided choices.