What Do Credit Card Numbers Start With?
Ever wonder what your credit card numbers mean? Learn how the initial digits reveal the card type, network, and issuing bank.
Credit card numbers often appear to be a random sequence of digits, yet they follow a highly structured system designed for security and efficient processing. These numbers are not arbitrarily assigned; instead, their initial digits carry specific meanings that identify the card’s industry, network, and even the issuing financial institution. Understanding this structure helps demystify how credit card transactions are routed and processed.
The First Digit’s Significance
The very first digit of a credit card number is the Major Industry Identifier (MII). This single digit serves to categorize the primary industry of the card issuer. It helps in the initial recognition of the card type.
Different MII digits correspond to various sectors. For instance, ‘3’ is typically for travel and entertainment, while ‘4’ and ‘5’ commonly denote banking and financial institutions. This system helps payment systems quickly identify the card’s general purpose.
Identifying Major Card Networks by Starting Digits
Beyond the first digit, the initial few digits of a credit card number identify the specific payment network. For example, Visa cards consistently begin with ‘4’.
Mastercard cards typically start with ’51’ through ’55’. American Express cards always begin with ’34’ or ’37’. Discover cards often commence with ‘6011’, ‘644’, or ’65’. Diners Club cards typically start with ’36’ or ‘300’ through ‘305’, and JCB cards frequently begin with ‘3528’ through ‘3589’. These specific sequences are fundamental for payment systems to correctly route transactions to the appropriate network.
The Issuer Identification Number
Following the Major Industry Identifier and network-specific prefixes, the subsequent digits form the Issuer Identification Number (IIN), also known as a Bank Identification Number (BIN). The IIN comprises the first six to eight digits of the credit card number.
This unique sequence identifies the financial institution that issued the card. For example, within the Visa network, while all cards start with ‘4’, the next five to seven digits pinpoint the issuing bank. The IIN is a critical component for transaction routing, fraud detection, and determining the issuing bank for chargeback processes.
The Full Structure of a Credit Card Number
The initial digits, including the MII and the IIN, are only the beginning of a complete credit card number. Following these identifiers is the individual account number, which is unique to each cardholder. This segment represents the bulk of the credit card number’s length.
The final digit of a credit card number is a check digit, often calculated using the Luhn algorithm. This digit serves as a simple checksum that helps validate the entire number. It is a basic integrity check designed to detect common errors, such as mistyping a digit.