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, ...

Luke Durant, a researcher and amateur mathematician, has identified the largest new prime number known to humankind. The newly discovered prime number is 2 to the power of 136,279,841, then minus one.