The largest prime number known is 2 74,207,281− 1, a number with 22,338,618 decimal digits.
It was found in 2016 by the Great Internet Mersenne Prime Search (GIMPS).
The earlier largest prime number, a natural number that can be divided without a remainder by 1 and itself, was discovered on 25 January 2013 by Curtis Cooper (USA).
The number is 257,885,161-1 and contains 17,425,170 digits.
The Great Internet Mersenne Prime Search (GIMPS) currently offers a US $3000 research discovery award for participants who download and run their free software and whose computer discovers a new Mersenne prime having fewer than 100 million digits.