A credit card number is the long set of digits displayed across the front or back of your plastic card. It is typically 16 digits in length, often appearing in sets of four. Sometimes it can be as long as 19 digits, and it is used to identify both the credit card issuer and the account holder.

Credit card numbers are not randomly assigned. They’re coded so that they identify the issuer, to help prevent identity thieves from simply guessing at account numbers and committing fraud. The credit card number must fit a complex pattern in order to work.

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Fun Facts About Credit Card Numbers

  • Credit card numbers are created using a system from the American National Standards Institute, or ASNI.
  • The first six numbers are used to identify the credit card issuer. And the first digit is known as the Major Industry Identifier, or MII.
  • Here are some popular MIIs:
    • Travel and entertainment cards, such as American Express, begin with the number 3
    • Visa cards begin with 4
    • MasterCards begin with 5
    • Discover cards begin with 6
  • Following the numbers that identify the issuer are the numbers that identify the account holder.
  • Each issuer has one trillion possible numerical configurations with which to create account numbers.
  • Different credit cards use slightly different numbering systems. With Visa, for instance, digits two through six are the bank number. With MasterCard, the bank number appears in digits two and three, two through four, two through five, or two through six. In contrast, American Express uses digits three and four to specify the type of card and currency used.
  • The last digit of a credit card number is known as a check sum. It is a key that shows whether a credit card is indeed valid. The check sum is created by a formula known as the Luhn algorithm.
  • Inventor Peter Luhn, an IBM engineer who played a role in the early development of the internet, created the Luhn algorithm. Luhn’s complex algorithm is also used in automobile VINs, bar codes, ISBN numbers on books and magazines, and U.S. bank routing codes.
  • The Luhn algorithm is able to immediately detect errors when people inaccurately transcribe credit card numbers. It can tell, for instance, when someone accidentally hits the 9 key instead of the 6 key, as well as many other common errors.

Nothing About a Credit Card Number Is Random

As you can see, credit card companies are not just throwing digits out randomly.Every credit card comes with a unique set of numbers with a utilitarian purpose.

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Legal Disclaimer: This site is for educational purposes and is not a substitute for professional advice. The material on this site is not intended to provide legal, investment, or financial advice and does not indicate the availability of any Discover product or service. It does not guarantee that Discover offers or endorses a product or service. For specific advice about your unique circumstances, you may wish to consult a qualified professional.

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