The conjecture that every even integer greater than 2 is the sum of two primes. Goldbach’s conjecture remains one of the most famous unsolved problems in number theory. The conjecture was first made in 1742 in a letter from Chirstian Goldbach to Euler. Computer calculations have verified the conjecture up to 1018. In 1937, Vinogradov showed that all sufficiently large odd numbers can be written as the sum of three primes. In 1973, Chen showed that every sufficiently large even number can be written either as the sum of two primes or as the sum of a prime and the product of two primes.