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Credit cards that are part of the Visa, Mastercard and Discover payment networks have 16 digits, while those that are part of the American Express payment network have just 15. There are also other numbers on the front or back of your credit card that can be used to authenticate transactions.
What Do All the Numbers on Your Credit Cards Mean?
While all of the numbers on your credit card can appear to be random, there's actual meaning behind them. For example, if your credit card numbers begin with 3, then it's always part of the American Express, Diner's Club or Carte Blanche payment networks. If the card begins with a 4, then it is a Visa. Card numbers that begin with 5 are part of the MasterCards, while cards that begin with 6 belong to the Discover network.
The next five digits can be used to identify the card issuer, such as the bank or credit union, as well as the specific credit card product you are using. For example, all Chase Visa Signature cards like the Chase Sapphire Reserve® and Chase Freedom Unlimited® begin with the numbers 414720.
The rest of the 15 or 16 digits are unique and linked to cardholder's account number. These last one or two numbers are "check digits." Check digits are applied to a formula that helps determine if your credit card number is actually valid. With this formula, a computer can quickly determine if any credit card number is valid.
Credit Card Numbers Versus Account Numbers
Interestingly, the number on your credit card isn't actually your account number, though the two are linked. Your account number will often appear on your credit card statement, and you will need to reference it to make payments. If your card is lost or stolen, then you'll receive a replacement card with new credit card numbers, but your account number will remain the same. Also, every American Express card has unique numbers, even among authorized user cards that are issued from the same account. In contrast, authorized user cards from other payment networks will have the same numbers when they are linked to the same account.
What About Those Other Numbers?
Credit cards also have another three-digit number that usually appears on the back of the card in the signature panel. These numbers can be called CVC numbers (Card Verification Code), but they also go by other names. Their purpose is to provide another level of verification when you make a purchase where the card isn't present, such as a telephone or online transaction. American Express cards also have a four-digit number on the front that serves the same purpose, called a CVV (Card Verification Value).
How to Protect Your Credit Card Numbers
Now that you know what all of these numbers mean, you need to know how best to protect them. First, you should always be careful when taking pictures that show your credit card number. Modern still and video cameras have very high resolution, and someone could enlarge a picture to read a credit card number, even if the card isn't very big in the image. If you need to include your credit card in a picture, be sure to cover up as many digits as possible. Since the first six digits are not unique to your card, be sure to cover up the remaining nine or ten digits, if not all of them.
You should also avoid writing down your credit card numbers, as this information could be used fraudulently, just like your actual credit card. And if your credit card is lost or stolen, be sure to report it to your card issuer. Nearly all card issuers will send you a replacement card at no cost, and many will ship it for free via overnight mail if you request it.
Now you know what those long credit card numbers mean. The next step is protecting your card numbers and your cards so this information doesn't fall into the wrong hands.