Goldbach conjecture, in number theory, assertion (here stated in modern terms) that every even counting number greater than 2 is equal to the sum of two prime numbers. The Russian mathematician Christian Goldbach first proposed this conjecture in a letter to the Swiss mathematician Leonhard Euler in 1742. More precisely, Goldbach claimed that “every number greater than 2 is an aggregate of three prime numbers.” (In Goldbach’s day, the convention was to consider 1 a prime number, so his statement is equivalent to the modern version in which the convention is to not include 1 among the prime numbers.) Goldbach’s