As it turned out, the maximum possible number in the game is about 10^300. At higher values the game stops working. This can not be called a game engine problem (the game is made in Game Maker Studio) because 10^300 is a very very large number. However, Realm Revolutions is an incremental game and sooner or later super-large numbers may appear in it.
In this update (v0.16), all operations with numbers has been rewritten, and now the numbers can be as large as possible.
Such update does not add new content, but with this update it will be possible to add new things to the game, without fear that later we will reach the limit of gold or food. So I think this update is quite important and that work had to be done before adding new content.