# How Long Are Credit Card Numbers?

Do you know how long credit card numbers are? If you’re not sure, you’re not alone. Many people don’t know the answer to this question.

In this blog post, we’ll tell you everything you need to know about credit card numbers, including how long they are and where you can find them.

We’ll also share some tips on how to keep your credit card number safe. So if you’re curious about credit card numbers, read on!

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## The Length of Credit Card Numbers

Credit cards typically have 16 digits. The first six digits are theIssuer Identification Number (IIN), which identify the card issuer. The next nine digits are the account number, and the final digit is the check digit. The check digit is used to validate the credit card number using the Luhn algorithm.

### Visa

Visa credit card numbers are 16 digits long. The first four digits are the card type indicator. The next eight digits identify the cardholder’s account number. The last four digits are called the check digit, and they’re used to verify that the credit card number is valid.

### Mastercard

Mastercard credit card numbers are 16 digits long. The first four digits are the bank identifier number (BIN), followed by the customer account number. The last digit is the check digit, used to verify that the credit card number is valid.

### Discover

Discover credit cards have 16-digit numbers. The number is divided into four four-digit sections, and each section is separated by a space. The first four digits are the Issuer Identification Number (IIN), which identifies the card issuer. Discover’s IIN ranges from 6011 to 6299. The next six digits are the account number, and the last four digits are the check digit, which is used to verify that the card number is valid.

### American Express

American Express credit card numbers all start with ’37’. The number of digits in the card number is 15.

## Why Do Credit Card Numbers Have Different Lengths?

Credit card numbers have different lengths because they are generated using a mathematical algorithm that creates a unique number for each card. The algorithm produces a number that is a combination of the account number, the bank identification number, and the individual card number. The length of the credit card number is determined by the number of digits in the algorithm.

### The Luhn Algorithm

The Luhn algorithm or Luhn formula, also known as the “modulus 10” or “mod 10” algorithm, is a simple checksum formula used to validate a variety of identification numbers, such as credit card numbers, IMEI numbers, National Provider Identifier numbers in the United States, Canadian Social Insurance Numbers, and Israel ID Numbers.

The algorithm was created by IBM scientist Hans Peter Luhn in 1954. It is in the public domain and is in wide use today. It is not intended to be a cryptographically secure hash function; it was designed to protect against accidental errors, not malicious attacks. Most credit cards and many government identification numbers use the algorithm as a simple method of distinguishing valid numbers from randomly selected invalid ones.

The Luhn formula is calculated by doubling every second digit from right to left and adding the individual digits of the products together:

For example, for the number 41234567890:

1×2 + 2×2 + 3×2 + 4×2 + 5×2 = 1+4+6+8+10 = 29

9×1 + 0×2 = 9

Sum: 29 + 9 = 38
Then add all single digits together: 3+8=11<- this number doesn't end in 0 so it's not a valid credit card number according to the Luhn check.

### The IIN

All credit card numbers start with a six-digit issuer identification number (IIN). The IIN is sometimes referred to as the bank identification number (BIN). These six digits are used to identify the financial institution that issued the card to the cardholder.

The first digit of the IIN is known as the major industry identifier (MII). The MII is used to identify the industry of the card issuer. The following table shows the MII digits and corresponding industries:

MII Digit| Industry
———|———-
0| Banking and financial
1| Airline
2| Aviation
3| Travel and entertainment
4| Banking and financial
5| Banking and financial
6| Merchandising and banking/financial
7| Petroleum
8| Telecommunications and banking/financial
9| National assignment

## How to Remember Your Credit Card Number

### The Mnemonic Device

One way to help remember your credit card number is by using a mnemonic device. A mnemonic device is a technique that helps you remember something by associating it with something else that is easier to remember. For example, you might associate your credit card number with your birthday or your mother’s maiden name.

To use this technique, you will need to break your credit card number down into smaller chunks that are easier to remember. For example, if your credit card number is 1234-5678-9012-3456, you might break it down into four groups of four numbers: 1234, 5678, 9012, 3456. Then, you would associate each group of numbers with something else that is meaningful to you.

For example, you might associate the first group of numbers (1234) with your birth year, the second group of numbers (5678) with the street where you grew up, the third group of numbers (9012) with your mother’s maiden name, and the fourth group of numbers (3456) with your father’s middle name.

Once you have associated each group of numbers with something else that is meaningful to you, try to create a sentence or phrase that will help you remember the association. For example, “My birth year is 1234 and I grew up on 5678 Street. My mother’s maiden name was 9012 and my father’s middle name was 3456.”

If you can remember the sentence or phrase, you should be able to recall the credit card number when you need it.

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