What is the theory that states any sufficiently large even number can be expressed as the sum of two prime numbers?

The theory that states any sufficiently large even number can be expressed as the sum of two prime numbers is known as Goldbach's Conjecture. This conjecture has intrigued mathematicians for centuries and specifically addresses the relationship between even integers and prime numbers.

Goldbach's Conjecture posits that every even integer greater than two can be represented as the sum of two primes. While this has been tested for very large numbers and holds true in those cases, it has not been conclusively proven for all even numbers, making it one of the oldest unsolved problems in number theory.

The other theories mentioned are unrelated to this particular conjecture. Fermat's Last Theorem deals with the impossibility of finding integer solutions for certain equations, the Pythagorean Theorem pertains to the relationship between the sides of right triangles, and the Riemann Hypothesis is concerned with the distribution of prime numbers rather than their sum. Each of these concepts is significant in its own right, but they do not address the specific assertion made by Goldbach's Conjecture.