@11011110 I've asked the same question a couple of years ago because it is related to the certificate complexity of being a prime. It got the answer 47867742232066880047611079, see
mathoverflow.net/questions/316

@jsiehler How about the chromatic number of the plane? Easy to state with finite unit-distance graphs (assuming ZFC). en.wikipedia.org/wiki/Hadwiger

@11011110
I made some Smullyan-style metapuzzles using this observation for Sudoku many years ago. They were of the type that suppose that some fields are missing from a Sudoku puzzle, fill out the rest of it.

Mathstodon

The social network of the future: No ads, no corporate surveillance, ethical design, and decentralization! Own your data with Mastodon!