What is a credit card number and what does it mean?

Credit card numbers sometimes feel long and cumbersome to fill in when you're shopping online, but did you know that each of those digits is a critical part of any successful transaction? This 15 (sometimes 16) digit number is designed in a specific sequence to communicate vital authentication factors about the card member, issuing bank and credit card network.

This means that there are over 1 trillion possible credit card numbers for each card issuer!

In this article you will learn:

• What is a credit card number?
• What do credit card numbers mean?
• Where do I find my credit card number?
• How can I keep my credit card number safe?

What is a credit card number?

A credit card number is a sequence of digits assigned to individual card members that signals to merchants, issuers and networks that your credit card is a legitimate form of payment. It helps identify your information correctly and securely.

Although it may seem random, each of the digits in a credit card number is placed in a strategic order and follow a standard formula. The sequence and standardization of credit card numbers are maintained by the American National Standards Institute and the International Organization for Standardization (ISO). While these organizations sound a bit bureaucratic, their job is important—they ensure there are global and national standards that financial institutions follow so everyone speaks the same digital language. 

What do credit card numbers mean?

Each digit in a credit card number (or debit card number), has a specific meaning and acts as a unique identifier when grouped together. Let's break down what each digit means.

The first number

The first number is used to identify the industry and credit card network. There are four networks:

• American Express cards begin with the number 3, usually 34 or 37.
• Visa cards begin with the number 4.
• Mastercards begin with the number 5.
• Discover cards begin with the number 6.

Besides the payment network, the first digit also identifies which industry the card is associated with. This is called the Major Industry Identifier (MII) and is defined by the American Banking Association. The main MIIs are listed below by the digit they're associated with.

• 1 and 2 are cards associated with air travel and financial services
• 2 through 6 are cards associated with banking and financial
• 7 is the petroleum industry
• 8 is health care and telecommunications
• 9 for use by the government or “other" category 

The next 5 numbers

This set of numbers collectively identifies the financial institution, such as Chase, that is issuing the card. This section of your credit card number is called the Issuer Identification Number (IIN), also known as the Bank Identification Number (BIN).

The next 9-12 numbers

The next 9 to 12 numbers identify the unique card member and account associated with the card.

The last number

The last digit serves as a final check for payment processors. Sometimes called the checksum, it's a way to verify that a card number is real.

Where do I find my credit card number?

Your credit card number will either be on the front or back of your credit card and appears in groups of three or four digits with spaces in between the groups. It is generally printed above the expiration date, shown as 00/00, as well as the three-digit security code. If you don't have your card in front of you but need to find your number, you may find it by signing into your online account.

How can I keep my credit card number safe?

Most credit card issuers offer different forms of fraud protection to ensure no one is using your credit card number without your permission. There are other ways that you, the card member, can protect your credit card number from fraudsters.

• Create an online credit card account with your credit card issuer and turn on suspicious activity alerts.
• Take advantage of multi-factor authentication when it's offered.
• Don't click on suspicious links that may be phishing for credit card numbers on your computer. 
• Sign up for paperless statements and make payments online to remove your sensitive information from the postal system. 
• Shred any documents with sensitive personal information, instead of throwing them in the trash. 
• When shopping online, use secure sites only (https), and confirm that the web address includes the company's correct name. 
• Type out your credit card number for each transaction. While many people find it convenient, it's never a best practice to store your credit card number with an online retailer or other site. 

Be vigilant about where you keep your physical card or access to the card number to prevent attempts at fraud. If you do lose your card or see suspicious activity, call your credit card issuer immediately to freeze your account.

In conclusion

While seemingly random, credit card numbers are carefully assigned to each new card member. Like a traffic controller, each digit signals who and where to send transaction information. The sequence of digits is packed full of traffic patterns linking specific banks, networks and card members.