Card numbers exist to properly identify your card, as well as to increase security. (GETTY IMAGES)
Key Takeaways
- Your credit card number usually consists of 15 or 16 digits, depending on the issuer.
- Every number of your credit card account conveys information, such as the industry, routing information for the account and whether the credit card account number is valid.
- The CVV, or card verification value, is a three- or four-digit number that you're asked for when you use your credit card online or over the phone.
Most of us are curious beings by nature. So, if you've been staying awake at night wondering what your credit card number means, it's your lucky day.
I'm going to pull back the curtain and show you not only what the numbers represent, but also how they're designed to catch an invalid credit card account number. I know the suspense is killing you, so let's get to it.
How Many Numbers Are on a Credit Card?
There are standards for the account numbers, and this falls under the purview of the International Organization for Standardization. The ISO is an independent nongovernmental international organization. The enforcement of the ISO's standards is done by the American National Standards Institute.
You'll find your credit card number either on the front or on the back of the card. Credit cards usually have 15 or 16 account numbers. Each digit conveys identifying information about the credit card, and the assigned numbers must follow the guidelines set by the ISO. However, there is some variation in the way the standards are applied.
The First Number
This number is called the MII, or major industry identifier, and it specifies the card network and industry. If your card starts with 3, your card uses the American Express network. Visa starts with 4, a Mastercard is 5 and Discover is 6.
Other numbers are used to identify the industry. For instance, 1 and 2 are used for the airline industry. The numeral 3 represents travel and entertainment, so it makes sense that 3 also indicates it's an American Express card. (AmEx cards largely focus on travel.) The table below shows the industry associated with the first digit of a credit card number.
| FIRST DIGIT OF A CREDIT CARD NUMBER | INDUSTRY |
| 1 | Airlines |
| 2 | Airlines and financial |
| 3 | Travel and entertainment (including American Express) |
| 4 | Banking and financial (Visa) |
| 5 | Banking and financial (Mastercard) |
| 6 | Merchandising and banking (Discover) |
| 7 | Petroleum |
| 8 | Health care and communications |
| 9 | Government |
Numbers 2 to 6
This group of numbers is called the issuer identification number. Generally, these numbers help identify the credit card company or institution that issued the credit card.
But note that different credit cards might have slightly different numbering systems. For instance, Visa uses the second through sixth numbers for the bank number. But American Express uses the third and fourth digits to identify the type of card and currency used.
Numbers 7 Through 15 (or More, Depending on the Length of the Account Number)
There's a common misconception that your credit card number reflects your actual credit card account number. Your account number is found starting at around digit seven or eight. The numbers in this group are unique to an issuer, and they help with routing the information to the proper channels.
The Last Digit
The caboose of the card number has an important role. It's called the check digit, and it's designed to make sure all the account numbers represent a valid credit card number.
Payment processors use a checksum formula called the Luhn algorithm. It was invented by Hans Peter Luhn of IBM. It's used to determine if the credit card numbers have a logical pattern. If the numbers don't work with the algorithm, it isn't a valid credit card number.
Where Is the Security Code on a Credit Card?
This is a three- or four-digit number, and it's often called the CVV, or card verification value. The CVV will be either on the front or the back of the card. The location of the CVV depends on the network payment processor that's used.
| NETWORK PAYMENT PROCESSOR | LOCATION OF CVV |
| Visa, Mastercard and Discover | A 3-digit CVV that's on the back of the credit card |
| American Express | A 4-digit CVV that's on the front of the credit card |
The CVV is designed to increase security, since you'd most likely need to have the card in your hand to know this code number. For instance, if someone stole your credit card number and tried to purchase something online, unless the thief knows your CVV, that person won't be able to complete the purchase.
This code also may come into play when you order a pizza by phone. You give the credit card number, and the restaurant employee asks for the expiration date and the CVV. This is easy to answer, of course, if you're looking at the actual credit card.
This isn't foolproof by any means. It's possible a thief could have your physical card and have access to the CVV. But the security code does provide another layer of security against some kinds of fraud. In particular, it combats what's called "card-not-present fraud," or CNP fraud, which can occur online and on the phone.
So, be sure you guard your CVV number. And when you do share it, make sure you're on a secure website or on a phone call that you initiated.
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