What Is a Credit Card Number (CC# / CCN)?

A Credit Card Number, also known as a payment card number or primary account number (PAN), is a unique numeric identifier assigned to a credit card or payment card. It is a crucial component of payment card transactions and serves as a reference to identify the cardholder's account.

Structure of a Credit Card Number

Issuer Identification Number (IIN):

The first 6 digits of a credit card number are known as the Issuer Identification Number (IIN), or sometimes the Bank Identification Number (BIN). This segment identifies the institution that issued the card and ties it to a specific card network (such as Visa, Mastercard, American Express, etc.).

Account number

Following the IIN, the next set of digits (usually up to 9 or 12 digits depending on the card) is the individual account number. This is unique to the cardholder and is assigned by the issuing bank. It differentiates your card from millions of others, even those issued by the same bank or under the same network.

For example, if your card number is 16 digits long and the IIN takes up the first 6 digits, the next 9 digits might represent your personal account number, leaving the final digit as the check digit.

Check digits

The last digit in the credit card number is the check digit, calculated using the Luhn algorithm. This mathematical formula is designed to detect errors in the number (like a mistyped digit). When a credit card number is entered into a system, the Luhn algorithm uses the other digits to verify that the number is valid.

If the check digit doesn’t match what the algorithm expects, the number is flagged as invalid, helping prevent errors and catch fake card numbers.

Common Credit Card Number Lengths and Starting Digits

Credit card numbers vary slightly in length and format depending on the card network, but most follow well-established standards. Here's a breakdown of the most common lengths and the starting digits (also called leading digits) that help identify the card type.

Common Credit Card Number Lengths

• Visa: 13, 16, or 19 digits
• Mastercard: 16 digits
• American Express: 15 digits
• Discover: 16 digits
• Diners Club: 14 digits
• JCB: 16–19 digits

While 16 digits is the most typical credit card number format overall, specific card types—especially those used internationally or for corporate purposes—may differ slightly.

Security Features​

While the structure of a credit card number plays a role in identification and validation, additional security features are built into credit cards to help prevent fraud and unauthorized use. These features work together to protect both consumers and merchants during physical and online transactions.

CVV/CVC (Card Verification Value/Code)

The CVV (Visa, Discover) or CVC (Mastercard) is a 3-digit number printed on the back of most cards, usually near the signature strip. For American Express, it’s a 4-digit code printed on the front.

• Used primarily for online or over-the-phone purchases
• Not stored by merchants, which helps prevent misuse if their databases are breached

EMV Chip

The EMV chip (Europay, Mastercard, and Visa) is a small metallic square embedded in the front of most modern credit cards.

• Generates a unique, one-time code for each transaction
• Provides far greater protection than magnetic stripes against counterfeit fraud
• Has become standard for in-person transactions globally

Magnetic Stripe

Still found on many credit cards, the magnetic stripe holds static data about the card, including the card number and expiration date.

• Considered less secure than EMV chips
• Being phased out in many countries, but still used for legacy systems

Holograms and Signature Panels

• Holograms: Small 3D images (like the dove on Visa cards) are hard to replicate and help verify authenticity.
• Signature panels: Cards often include a signature strip for cardholder identification and fraud prevention.

Contactless Payment Technology (NFC)

• Enables tap-to-pay functionality using Near Field Communication (NFC)
• Uses tokenization to encrypt card details, improving security
• Common on newer cards and mobile wallets (e.g., Apple Pay, Google Pay)

Tokenization & Encryption (Digital Wallets)

When cards are used in mobile wallets, actual card details are replaced with a token—a randomly generated string of data—used to process transactions securely.

• Helps prevent theft of card details during digital transactions
• Adds an extra layer of security for online and mobile purchases

Related Terms

Understanding credit card numbers also means being familiar with a few related terms that often come up in financial and payment discussions. These terms help explain how credit cards function and how they're used in both physical and digital environments.

Card Issuer
The bank or financial institution that provides you with the credit card (e.g., Chase, Citi, Capital One).

Card Network
Processes transactions and sets rules for payments. Examples: Visa, Mastercard, American Express, Discover.

CVV/CVC
The 3- or 4-digit security code used for verifying purchases, especially online or over the phone.

Expiration Date
The date printed on the card indicating when it is no longer valid.

Magnetic Stripe
The black strip on the back of the card that stores data; now being phased out in favor of chip technology.

EMV Chip
A small chip embedded in your card that creates a unique code for each transaction, making it harder to clone.

Tokenization
Replaces your real card number with a random code (token) during digital transactions for added security.

Card-Not-Present (CNP)
Transactions made without the physical card—like online or phone orders—that require extra verification.