Question

which number is not prime? 38 2 23 31

Explanation:

Step1: Recall prime number definition

A prime number is a number greater than 1 that has no positive divisors other than 1 and itself.

Step2: Check each number

• For 2: Divisors are 1 and 2, so prime.
• For 23: Divisors are 1 and 23, so prime.
• For 31: Divisors are 1 and 31, so prime.
• For 38: \( 38 = 2\times19 \), so it has divisors 1, 2, 19, 38. Not prime.

Answer:

38