https://en.wikipedia.org/wiki/Payment_card_number https://en.wikipedia.org/wiki/Payment_card_number >The first (leading) digit of the IIN identifies the major

https://en.wikipedia.org/wiki/Payment_card_number https://en.wikipedia.org/wiki/Payment_card_number >The first (leading) digit of the IIN identifies the major industry of the card issuer. 4 and 5 stand for "Banking and financial". >The leading six digits of the card number is the issuer identification number (IIN), sometimes referred to as the "bank identification number (BIN)". There's a list of all 1000000 possible IINs/BINs, but it's not publicly available: >The official "ISO Register of Issuer Identification Numbers", is not available to the general public. It is only available to institutions who hold IINs published in the Register, financial networks and processors. Institutions are required to sign a licensing agreement before they are given access to the Register. Several IINs are well known, especially those representing credit card issuers. It's a bit like IP address blocks: there's is/was some logic to it, but to actually know which bank a IIN/BIN belongs to (after mergers, acquisitions etc) you have to look it up in the register.