The International Bank Account Number (IBAN) is a standardized way to identify bank accounts across borders. It consists of a 2-letter country code, 2 check digits, and a country-specific BBAN (Basic Bank Account Number).
Validation uses MOD-97 as per ISO 13616: the IBAN is rearranged (move first 4 chars to end), letters converted to numbers (A=10..Z=35), and the result checked for remainder 1 when divided by 97.