1️. How Many Numbers Are on a Credit Card?
Most credit cards have 15 or 16 digits in total. These numbers aren’t random; each digit conveys specific information and must comply with standards set by the International Organization for Standardization (ISO).
2️. Major Industry Identifier (MII)
The first digit of a credit card number is called the Major Industry Identifier (MII). It indicates the card’s network and industry type. Here’s a quick look:
| First Digit | Industry & Network |
|---|---|
| 1 or 2 | Airlines & Financial |
| 3 | Travel & Entertainment (American Express) |
| 4 | Banking & Financial (Visa) |
| 5 | Banking & Financial (Mastercard) |
| 6 | Merchandising & Banking (Discover) |
| 7 | Petroleum |
| 8 | Health Care & Communications |
| 9 | Government |
So, if your card starts with 4, it’s likely a Visa, while 5 usually signals Mastercard.
3️. Numbers 2 to 6: Issuer Identification Number
These digits are known as the Issuer Identification Number (IIN) and help identify the specific institution that issued the card. While numbering can vary by network, for example:
- Visa uses digits 2-6 for bank identification.
- American Express uses digits 3-4 to specify card type and currency.
4️. Numbers 7 to 15 (or More): Account Identifier
These numbers are unique to each card and route transactions to the correct account. Contrary to popular belief, these digits represent a part of your account identifier rather than the full account number.
5️. The Last Digit: Check Digit
The final digit, called the check digit, plays an important role in security. It uses the Luhn Algorithm (developed by IBM’s Hans Peter Luhn) to verify the card’s validity. If the numbers don’t match this pattern, the card is flagged as invalid.
6. Where Is the Security Code (CVV)?
The CVV (Card Verification Value) is the three- or four-digit code located on the card:
- Visa, Mastercard, and Discover have a 3-digit CVV on the back.
- American Express has a 4-digit CVV on the front.
This code adds a layer of security, especially for “card-not-present” (CNP) transactions like online and phone orders. It helps prevent unauthorized purchases if only the card number is compromised.
Takeaway: Credit card numbers aren’t just random—they carry essential info for routing transactions and security. So, remember to keep your CVV private and only share it on secure websites or calls you initiated!