Question

Which number is prime?

A.
57

B.
63

C.
51

D.
59

Answer 1

D. 59 is the answer

Answer 2

It's D. 59, because all of the other numbers are divisible by 3, and you can tell by adding up the digits. (5 + 7 = 12, 3 × 4 = 12) (6 + 3 = 9, 3 × 3 = 9) (5 + 1 = 6, 3 × 2 = 6)