With the increase in ecommerce transactions in the UAE, credit card numbers continue to become more important while the physical card becomes less so. But what do all those numbers mean? It is quite simple actually, every digit of your card number means something.
Visa
A standard Visa credit card has a 16 digit number, although nowadays some are issued with 13 to 19 digits. The first digit always starts with a 4. The next five numbers are a specific code that denotes the bank who issued this card. The remaining digits are your account number and the last digit is the check number. The check number is based on a mathematical formula called the Luhn algorithm. This formula is used in a variety of identification numbers to distinguish a valid number from an incorrect or mistyped one.
MasterCard
The first digit of a MasterCard credit card starts with 5. The next four digits identify the bank issuer, while the remaining digits also consist of the account number and check digit.
American Express
American Express credit cards always start with the digits 34 or 37. The third digit identifies the type of American Express card, while the fourth digit denotes the currency the card is issued in. Again, the remaining digits consist of the account number, with the last digit being the check number.
Other Cards
Discover credit cards have a similar card number structure but start with the number 6. Diner’s Club credit cards start with the number 3.
Cool Trick
You can quickly check if a 16 digit card number is valid with some simple math. Starting with the first digit, multiply each alternating number by 2. If you get any doubledigit numbers, add the two digits so that you get one number. For example, if one of the digits is 5 and you multiply it by 2 to get 10, you add the 1 and 0 to get 1. Basically, you will have to do this anytime you multiply any number between five to nine by 2. You then sum up all these numbers. Next, add up all the alternating digits that you did not multiply by 2. If you add up the two totals, and they are divisible by 10, then you have a valid credit card number. Otherwise, it is a fake!
Here is an example:
Card Number: 
4 
3 
2 
1 
5 
6 
7 
8 
9 
0 
1 
2 
1 
2 
3 
4 

Alternate Numbers x 2 and sum 
8 
+ 
4 
+ 
(1+0) 
+ 
(1+4) 
+ 
(1+8) 
+ 
2 
+ 
2 
+ 
6 

37 
Sum remaining numbers 

3 
+ 
1 
+ 
6 
+ 
8 
+ 
0 
+ 
2 
+ 
2 
+ 
4 
26 
The sum of the two totals is 63, since this is not divisible by 10, the card number is a fake.
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