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The number 2,147,483,647 (two billion one hundred forty-seven million four hundred eighty-three thousand six hundred forty-seven) is the eighth Mersenne prime, equal to 231 − 1. It is one of only four known double Mersenne primes.
The primality of this number was proven by Leonhard Euler, who reported the proof in a letter to Daniel Bernoulli written in 1772. Euler used trial division, improving on Cataldi's method, so that at most 372 divisions were needed. The number 2,147,483,647 may have remained the largest known prime until 1867.
Barlow's prediction
In 1811, Peter Barlo...