How Many Numbers Are in a Card Number?
Unravel the mystery behind payment card numbers. Learn about their standard lengths, internal structure, and how they identify you securely.
Credit card numbers serve as unique identifiers for financial transactions, facilitating secure and efficient payments. These sequences of digits are not random; they follow a structured format designed to convey specific information about the card and its holder.
The Standard Length of Card Numbers
Most payment cards feature a number that ranges from 13 to 19 digits. While 16 digits are the most common length for credit cards issued by major networks, this is not a universal standard. Some cards may have 15 digits, while others can extend up to 19. This variation in length depends on the issuing network and the specific product. The consistency in format across different cards and issuers adheres to international standards, ensuring global interoperability for payment systems.
Understanding Card Number Components
A credit card number is composed of several distinct parts, each providing crucial information. The initial digits form what is known as the Issuer Identification Number (IIN) or Bank Identification Number (BIN). This segment, typically the first six to eight digits, identifies the financial institution that issued the card. The very first digit of the IIN/BIN often indicates the Major Industry Identifier (MII), classifying the industry of the card issuer, such as banking and financial services.
Following the IIN/BIN, the subsequent digits constitute the individual account number. This part uniquely identifies the cardholder’s account with the issuing bank. While the IIN/BIN identifies the issuer, the account number points to the specific customer and is used by the issuing entity to link the card to the customer’s designated bank accounts.
Variations Across Card Networks
The length and starting digits of card numbers vary among different payment networks.
Visa
Visa cards begin with a ‘4’ and are usually 16 digits long, though some can be 13 digits.
Mastercard
Mastercard numbers start with a ‘2’ or ‘5’ and are 16 digits in length.
American Express
American Express cards start with a ’34’ or ’37’ and have a 15-digit format.
Discover
Discover cards start with a ‘6’ and are 16 digits long, with common prefixes including ‘6011’, ‘644-649′, and ’65’.
These specific starting digits allow payment systems to quickly identify the card network and route transactions.
The Role of the Check Digit
The final digit of a credit card number is known as the check digit, and its purpose is to validate the entire card number. This digit is mathematically determined using the Luhn algorithm. The Luhn algorithm is not designed for cryptographic security, but rather to detect accidental errors, such as mistyped or transposed digits, during data entry.
The algorithm works by performing a series of calculations on the preceding digits of the card number. If the final sum derived from these calculations, including the check digit, is divisible by 10, the card number is considered potentially valid. This method helps to ensure data integrity, reducing the likelihood of processing invalid or incorrect card numbers.