On this day, 26 years ago, June 1, 1999 (April 18, 1999, the lunar calendar), humans first discovered a prime number of more than one million digits 2^6972593-1. On June 1, 1999, humans first discovered a prime number of more than one million digits 2^6972593-1. This is the first prime number we know of with more than one million digits. To be precise, if this prime number is written in the decimal form we are familiar with, it has a total of 2,098,960 digits. As early as 300 BC in the ancient Greek era, the great mathematician Euclid proved that there were infinitely many prime numbers. French priest Marine Mersenne published his results in 1644. He claimed that 2p-1 is prime for p=2, 3, 5, 7, 13, 17, 19, 31, 67, 127 and 257, and that 2p-1 is a composite number for other primes p less than 257. Today we call a prime number of the form M_p= 2p-1 a Mersenne prime, and the M in M_p is the first letter of Mersenne's surname.