The online computer game “Is this prime?” tests a player’s knowledge of prime numbers—and just surpassed 2,999,999 attempts. Give it a whirl.

Prime numbers are whole numbers greater than 1 that are not divisible by any whole number other than 1 and itself. The first few are 2, 3, 5, 7, 11, 13 … To explain how the RSA algorithm works ...

Fortunately, Édouard Lucas developed a prime number test in 1878, later proved by Derrick Henry Lehmer in 1930. Their work resulted in an efficient algorithm for evaluating potential Mersenne ...