You don’t select this last digit, it is deterministic. In a typical sixteen digit credit card number, the first fifteen digits are determined by the issuing bank, but the last digit, called the check digit, is mathematically determined based on all the other digits. To try and minimize this, credit card numbers contain a check digit. Humans often make mistakes in transferal. All of this transmission can cause errors, especially considering that humans are involved. (Here you can find a more complete list of Issue Identifier Numbers)Ĭredit card numbers are often typed in, input, transferred and quoted. To the left is a (non-exhaustive) list of the some of the common card prefixes.Ĭards can be identified by their first few digits (try it out now, pull a few cards out of your wallet and look them up). Some cards are Visa, some Mastercard, some are American Express … Issuer The first few characters of the card number describe the type of card.
For obvious reasons, just any sixteen digits will not work, they follow pattern. These digits are the unique account number for the card. These, typically, have sixteen digits on the front. Most of us carry credit cards and ATM cards.
