Which of the following is not a prime number?
Choose the best answer from the options below:
A 17
B 39
C 23
D 31
B 39
To determine which of the options is not a prime number, we need to check if each number has factors other than 1 and itself.
Option A: 17
17 is a prime number because it only has factors 1 and 17.
Option B: 39
To determine if 39 is prime, we need to check if it has factors other than 1 and 39. We can check its factors by dividing it by numbers from 2 to its square root, which is approximately 6.24.
39 divided by 2 is not an integer.
39 divided by 3 is 13, which is an integer.
Therefore, 39 is not a prime number as it has a factor of 3.
Option C: 23
23 is a prime number because it only has factors 1 and 23.
Option D: 31
31 is a prime number because it only has factors 1 and 31.
Therefore, the answer is B, 39, as it is not a prime number.