>Hi all,
>
>can someone tell me how I can calculate the modulus 97 on a number with 23 digits ? It seems that the MOD function has a problem with the large number. Is there another option ??

You could use maths... subtract the largest value of 97*10**n that can fit your number... but do it as a string:

- have the original 23-digit number as a string.
- divide it into groups of, say, 6 digits each.
- find the mod(group1,97) of the leftmost group.
- add the digits you got to the second group
- find the mod(mod1*1000000+group2, 97)
- repeat that with 3rd and 4th group.