GRE Question of the Day (July 26th)

Math

A “Sophie Germain” prime is any positive prime number p for which 2p + 1 is also prime. The product of all the possible units digits of Sophie Germain primes greater than 5 is

A. 3

B. 7

C. 21

D. 27

E. 189

Correct Answer - D - (click and drag your mouse to see the answer)

Question Discussion & Explanation