As of February 2013[update], the largest known prime number is 257,885,161 − 1, a number with 17,425,170 digits.
Plot of the number of digits in largest known prime by year, since the electronic computer. Note that the vertical scale is logarithmic. The red line is the exponential curve of best fit: y = exp(0.188439 t - 362.591), where t is in years.
Many of the largest known primes are Mersenne primes. As of February 2013[update] the ten largest known primes are Mersenne primes, while the eleventh is the largest known non-Mersenne prime. The last 15 record primes were Mersenne primes.
The record passed one million digits in 1999, earning a $50,000 prize. In 2008 the record passed ten million digits, earning a $100,000 prize and a Cooperative Computing Award from the Electronic Frontier Foundation.Time called it the 29th top invention of 2008. Additional prizes are being offered for the first prime number found with at least one hundred million digits and the first with at least one billion digits.
The following table lists the progression of the largest known prime number in ascending order. Here Mn= 2n − 1 is the Mersenne number with exponent n. The longest record-holder known was M19 = 524,287, which was the largest known prime for 144 years. No records are known before 1456.
Anonymous discovery: no proof provided, so sometimes not counted as a record.
Anonymous discovery: no proof provided. Later proven prime by Pietro Cataldi in 1588, and that is sometimes listed as a record.