The new prime number was discovered by machine No. 5, a computer at the University of Central Missouri, an otherwise nondescript desktop computer, which took the trouble to multiply 74,207,281 twos together and subtract 1 and then to check that it was not divisible by any positive integer other than 1 and itself.
This is the 15th prime number found by the Great Internet Mersenne Prime Search, or Gimps, for short, a volunteer project that has been running for 20 years. “I’ve always been interested in prime numbers,” said George Woltman, who founded Gimps after he had retired. “I had a lot of time on my hands,” he said.