What Number Do Credit Cards Start With?

Credit card numbers serve as unique identifiers for financial accounts, used for secure and efficient transactions across various platforms. These numerical sequences are not random; they follow a structured format conveying specific information about the card and its issuer. Understanding this structure helps explain how these numbers function.

The Major Industry Identifier (MII)

The first digit of a credit card number represents the Major Industry Identifier (MII). This single digit categorizes the primary industry of the entity that issued the card. For instance, cards beginning with ‘1’ or ‘2’ are typically issued by airlines.

The MII broadly classifies the type of organization behind the card. Digits starting with ‘3’ are associated with travel and entertainment industries, such as American Express or Diners Club. Cards issued by banking and financial institutions predominantly start with ‘4’ or ‘5’. Telecommunications and national assignments often use ‘6’ as their MII.

Issuer Identification Numbers (IINs) and Card Networks

The initial six to eight digits of a credit card number form the Issuer Identification Number (IIN), sometimes called a Bank Identification Number (BIN). This sequence uniquely identifies the financial institution or organization that issued the card. The IIN routes transactions to the correct issuer for authorization.

Different credit card networks are identifiable by distinct ranges within these initial digits. Visa cards consistently begin with ‘4’. Mastercard numbers typically start with ’51’ through ’55’. American Express cards start with ’34’ or ’37’. Discover cards commonly start with ‘6011’, or within the ranges ‘644’ through ‘649’, or ’65’. These specific prefixes allow payment processors to quickly identify the card network and direct the transaction accordingly.

The Full Credit Card Number Structure

Beyond the Issuer Identification Number, the remaining digits identify the individual account holder. This portion of the number is unique to each cardholder and is assigned by the issuing financial institution. The length of this account-specific segment varies depending on the card network and issuer.

The final digit of a credit card number is typically a check digit. This digit is generated using an algorithm, such as the Luhn algorithm, which helps validate the entire card number’s accuracy. This check digit acts as a basic error detection method, preventing common input mistakes and ensuring the number is valid before processing a transaction.