Bug with Integers

[Arno K]

Today I thought of writing some simple programs to work with integers on my prime, so I first tried something like 7^23 MOD 143, the first part is correctly computed and gives 27368747340080916343. But then 7^23 Mod 143 on the real calculator, the PC and android deliver 23 (in Cas and Home) which simply is wrong as it must be 2, confirmed by xcas, my old and trusty (sad that it has defective keys) 49G+ and even Geogebra.
This is the first time that I encounter a mathematical error on the prime, but this renders it nearly unusable, as from now on I will clearly double-check every calculation that I do until I know that mistakes using numbers are fixed, unbearable.
I can live with bugs, find matching workarounds as long as the problems are not essential, but a device for doing maths has to correctly do what its main purpose (crunching numbers) is, especially when a function is built-in and quite simple to program.
Arno