Researchers have discovered a prime number dubbed M74207281, the longest prime number currently in the world, with 22 million digits reported newscientist.com.

To be a prime number the number has to be bigger than one and only divisible by one and itself. For example, the number 10 is not prime because it is divisible by 2 and 5. Mersenne primes, prime numbers taking the form 2p -1, where P is a prime, are rarer. “The first Mersenne primes are 3, 7, 31, and 127 corresponding to primes of 2, 3, 5, and 7 respectively,” according to dailymail.co.uk.

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,” Woltman said.

“The largest known prime number, newly discovered, is almost five million digits longer than the previous record-holder also found by GIMPS,” reported nytimes.com. “This immense number can only be practically written down in mathematical notation using exponents: 274,207,281 − 1.

“Just to add to the previous answers: Usually, part of the discovery of these mathematical curiosities is not the result itself, but the new or improved method for finding these new results. It’s not just about finding the number which is meaningless in itself, but it’s about showing that mathematical techniques have advanced so much that we can even show that these incredibly huge numbers are prime,” reported stackexchange.com.