 , this conjecture has been verified for all numbers up to formula_59 Weaker statements than this have been proven, for example, Vinogradov's theorem says that every sufficiently large odd integer can be written as a sum of three primes.Chen's theorem says that every sufficiently large even number can be expressed as the sum of a prime and a semiprime (the product of two primes).Also, any even integer greater than 10 can be written as the sum of six primes.