Which of the following numbers is a Mersenne prime?

A: 90

B: 27 - 1

C: 211 - 1

D: 15

B: 2⁷-1 = 127

Step-by-step explanation:

A Mersenne prime is a prime of the form 2^n - 1, where n is also a prime.

Among the answer choices, neither 90=2·3²·5 nor 15=3·5 is prime. Both 2⁷-1 = 127 and 2¹¹-1 = 2047 are of the right form, but 2047 = 23·89 is a composite number.

2⁷-1 = 127 is a Mersenne prime