Erdős–Moser equation

Unsolved problem in mathematics
Does the Erdős–Moser equation have solutions other than 11+21=31?

In number theory, the Erdős–Moser equation is

where m and k are restricted to the positive integers—that is, it is considered as a Diophantine equation. The only known solution is 11 + 21 = 31, and Paul Erdős conjectured that no further solutions exist. Any further solutions must have m > 10109.

Throughout this article, p refers exclusively to prime numbers.