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. The Greek mathematician Euclid may very well have proved, ...

Is 170,141,183,460,469,231,731,687,303,715,884,105,727 prime? Before you ask the Internet for an answer, can you consider how you might answer that question without a ...