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What is a Credit Card Number?

4 min read

Last Updated: August 2, 2024

Table of contents

Key Takeaways

Though seemingly random, credit card number sequences can tell you a lot about the card.
Credit card numbers include a major industry identifier, issuer identification number, and checksum, all of which help identify the credit card network, card type, and individual credit card.
Credit cards also have security codes that help protect you from fraud.

A credit card number is a long set of digits displayed across the front or back of your plastic or metal credit card. It’s typically 16 digits in length, often appearing in sets of four, and it’s used to identify both the credit card issuer and the card itself.

Credit card numbers aren’t randomly assigned; they’re coded to identify the issuer, the network, the account, and the unique card, all in an effort to prevent theft and fraud. The credit card number must fit a complex pattern in order to work.

Each issuer has a nearly endless amount of numerical configurations with which to create account numbers and different credit cards use slightly different numbering systems. The various number systems serve different purposes.

The first number

The first digit of a credit card number is known as the major industry identifier (MII), according to the Associated Press. This digit identifies a credit card issuer’s industry. Here’s each MII and the industry it represents:

1: Airlines

2: Airlines and credit card network (Mastercard)

3: Credit card network (American Express)

4: Credit card network (Visa)

5: Credit card network (MasterCard)

6: Credit card network (Discover)

7: Petroleum

8: Health Care and Communications

9: Government

The next five numbers

Credit card digits two through six make up the issuer identification number (IIN), according to Experian, which may also be called a bank identification number (BIN). This number identifies the credit card company that issued the card and its credit card network.

The next 9-12 numbers

All remaining digits in a card number, before the last one, represent the individual credit card account. If you get a new credit card, these numbers may change. Your account number may have as few as nine or as many as 12 digits.

Infographic: the next 9 numbers of a credit card number

The last number

The last digit of a credit card number acts as a “checksum”, according to the Associated Press. That means the number plugs into an algorithm to confirm that the credit card number has been entered correctly. The checksum, also known as the “check number” or “check digit” is based on a formula known as the Luhn algorithm.

The Luhn algorithm can help to detect errors when people inaccurately transcribe credit card numbers or other personal identification numbers, like a Social Security number.

Credit card numbers vs. account numbers

While credit card numbers and account numbers are related, they’re not always the same. Your credit card number refers to a specific card, but your account number is tied to your personal account. At some credit card companies, cardmembers with multiple credit cards might have several credit card numbers. However, the company might give you a single account number. You can find your account number on your credit card statement.

Note that at Discover, your credit card number and account number are one in the same. To safeguard your account information from fraud and theft, your credit card number will only appear on the physical card. Any communication from Discover will only list the last four digits of the account number (this includes your monthly credit card statement).

Where is the security code on a credit card?

Your credit card number isn’t the only important number on your credit card. The card verification value (CVV) is a three- or four-digit number that acts as a security code, making fraudulent transactions more difficult. While credit card issuers may differ, you can often find your credit card’s security code on the back, near the credit card number and signature.

Did you know?

You can compare Discover credit cards against other industry-leading cards to find the one that’s best suited for how you use it.

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As you can see, credit card companies aren’t just assigning digits randomly. Every Discover credit card comes with a unique set of numbers that serve a purpose.

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