Credit Card Number

The majority of credit card issuers (Visa and Mastercard) have 16 digits displayed across their cards. American Express has 15. The first six digits of the number indicate the Issuer Identification number or IIN. The first digit is the Major Industry Identifier or MII.

The following five digits refer to the specific issuing bank. It is with these numbers that the necessary exchange of information for every transaction can take place. Mastercard: 2 and 3; 2 to 4; 5; or 6Visa: 2 to 6American Express: 3 and 4 (indicating whether the card is Platinum, Delta, etc.)The next six numbers indicate the account number. Usually six in total, the number of digits can also reach up to twelve. This sequence of numbers is assigned to individual customers.Below see a shorthand visual representation of the above information:

The other important feature of the credit card is embedded within the numbers itself. Invented by scientist Hans Peter Luhn, it is a simple algorithm which is used to validate identification numbers. IMEI numbers, South African Identification numbers, and credit card numbers can all be deemed valid via the algorithm. Instead of malicious attacks—against which card companies employ more complex security methods—the Luhn algorithm is a check for accidental errors. Institutions use it to distinguish legitimate credit card numbers from mistyped ones. For instance, when users type their credit card digits into any online shopping website, the website will automatically determine if the number is invalid when a mistake is made. 

In addition to the number on the front of credit cards, the back of the card includes an expiry date (MM.YYYY format) and the CVV number. The Card Verification Value is a three or four-digit number which functions as another mode of verification and protection. When a card machine registers the CVV, further assurance is provided that the current user is the owner of the card and that it hasn’t been stolen.