What is a Credit Card Number? It’s Far From Random

Have you ever wondered if your credit card number is something totally random or if there is a system that determines what your number is?  Credit card numbers are pre-determined so that the credit industry can keep track of how many cards there are in what specific areas.

Let’s take a look at the question “what is a credit card number?”

Issuer Identifier

The first six digits of your credit card determine the issuer and are known as the Issuer Identification Number, or IIN.  The first set of the six digits will tell you the issuer of the card and the rest of the six digits will help identify which card from the issuer and where it’s from.  Each card has a determined length of digits.  For example:

IssuerNumber Code and RangeTotal Card Digits
American Express34xxxx, 37xxxx15
Discover6011xx, 622126-622925, 644xxx-649xxx, 65xxxx16

Major Industry Identifier

The very first digit of a credit card indicates the major industry, or the type of the credit card (Airlines, Travel, Banking, etc…), known as the Major Industry Identifier, or MIN.

  • 1 – Airlines
  • 2 – Airlines and future use
  • 3 – Travel and Entertainment and Banking/Financial
  • 4 – Banking and Financial
  • 5 – Banking and Financial
  • 6 – Merchandising and Banking/Financial
  • 7 – Petroleum (Gasoline) and future use
  • 8 – Healthcare and Telecommunications and future use
  • 9 – National Assignment

The Structure of a Credit Card

Sample Credit Card

What do the credit card numbers mean?

The structure of a credit card number varies by system. For brevity sake the three main credit cards are used for this example.

American Express:  The third and fourth digits are type and currency. The fifth through eleventh digits are the actual account number. The twelfth through fourteenth digits are the card number within the account and the last digit is the check digit.

Mastercard:  The second and third digits, second through fourth, second through the fifth or the second though to the sixth digit (depending on what the second digit is) is the bank number. After the bank number is the account number and the final digit is a check digit.

Visa:  The bank number includes the second through sixth digit. The seventh through the twelfth or seventh through the fifteenth is the account number. The thirteenth or sixteenth is a check digit.

The final digit is always referred to as the check digit which is the same as a checksum.  An algorithm is used to arrive at a check digit and this is known as the Luhn algorithm. This was named after Hans Peter Luhn (1896-1964) who was awarded a patent for this in 1960. Luhn was an IBM scientist.  The formula is used to check that the card number is valid and has no errors.

More Credit Card Info

The Stripe on the Back of a Credit Card –  This magnetic stripe is often referred to as a magstripe. This is made up of iron-based magnetic particles in a plastic film.  Each particle is a tiny bar magnet that measures 20-millionths of an inch in length. There are three tracks on each magstripe and they are used by banks. These tracks are:

First track – holds 79-6 bit parity bit read-only characters.

Second track – holds 40 4-bit parity bit characters.

Third track – holds 107 4-bit parity bit characters.

Chances are your credit card uses only the first two tracks. The third one is a read/write track which is not standardized among banks. This third track generally has an encrypted PIN, currency units, amount authorized and the country code.

Smart Cards – A smart card involves cryptography (secret codes) and they have a microprocessor built right in. Cryptology is important to how these cards function. The user must corroborate his or her identity to the card every time a transaction occurs.  (Much the same as a PIN at an ATM.)

The smart card also executes a sequence of encrypted sign exchanges to ensure that each transaction is legit.  Once this has occurred only then will the transaction be carried out to completion. This protects the user from having their credit card information being picked up by a third party. This elaborate protocol is executed in a way that it is invisible to the user, with the only exception of entering a PIN to begin the transaction.

There you have it.  That is what a credit card number is.  Now if you ever feel like issuing your own credit cards you know how to set the numbers up (and if you have the funds to start up a credit card company, shoot me an email, we should talk).

Source: Wikipedia

Free Newsletter to Keep you Free From Broke!Name: Email: We respect your email privacyPowered by AWeber email marketing
Published or updated April 13, 2013.


  1. I just learned about the first couple number identifier yesterday! I actually didn’t even believe the person and took out my wallet lol…they were right

    • Haha, I did the same thing as I was editing the article. I kept pulling out my cards to see if the information was true.

  2. Yo demystified the the whole credit card numbering system! I am always interested in these types of things. A number of years ago, I found out the basis for the Social Security numbers. Now I Know what part of the country the card was issued.

  3. Pretty neat stuff. I don’t know whether to be impressed that there is actually a method behind the (seeming) madness, or a little disturbed that someone with the right sources (and arguably, too much time) could figure out so much just from the card number itself.

    • When you think about it, there has to be some system that all the credit card companies are agreeing to use. Otherwise you run the risk of two companies issuing the same number. But I wouldn’t have thought that the number sequences broke out specifically like they do.

What Do You Think?