Credit and Debit Card Number Formats

​Credit and debit card numbers follow specific formats to ensure proper identification and security. Typically, these numbers range from 13 to 19 digits. The first digit, known as the Major Industry Identifier (MII), indicates the card network and industry. The next six to eight digits form the Issuer Identification Number (IIN), identifying the issuing bank. The remaining digits, except the last one, are the individual account identifier. The final digit is a check digit, calculated using the Luhn algorithm to validate the card number. For example, Visa cards start with a 4 and have 16 digits, while American Express cards start with 34 or 37 and have 15 digits.

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