Cash

Cash is stored as a 32-bit signed integer, and as such overflows after 2,147,483,647. Earning 1 cash more than 2,147,483,647 causes the cash value to go to -2,147,483,648. Further addition of cash causes the negative value to go towards zero (e.g. earning 500 cash while at -2,147,483,648 results in -2,147,483,148), while spending cash while you have a negative value (interestingly, the game does allow you to do this) can bring you back to a positive value.

Cash stored as tax revenue and in the planetary back will also overflow after 2,147,483,647.

The most cash that can be granted at once with the SYS CASH command is 2,147,483,647. Any values higher than this are treated the same as entering SYS CASH 0