A significant part of the world - all of the EU, but also a lot outside it- uses the IBAN standard [0]. The checksum algorithm is mod97, two digits indeed. Very often, there are two checksums though!

Also, in my native Belgium, bank payments have had automated payment processing structured messages attached to almost all {b,c}2b payments. That one contains a similar mod97 check.

[0] https://en.wikipedia.org/wiki/International_Bank_Account_Num...