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BANKING: The numbers on your credit cards are not random! There is a logic behind all credit card numbers.

All credit cards follow the Luhn algorithm:

1. Starting from the first digit, double every alternate digit

2. If the multiplication results in a two-digit number, add both its digits together.

3. Add all these numbers and the digits we didn’t double in Step 1

4. The sum should be divisible by 10

Let’s run it on the card in the image: 5412 7512 3412 3456


broken image

Step 1: Result (10)422 (14)522 6422 64(10)6

Step 2: Result 1422 5522 6422 6416

Step 3: Result: 54

As the result is not divisible by 10, it is not a valid card number.

This algorithm is not intended to detect fraud, but only for typing errors. It can detect a single digit error and most adjacent digit swaps error.

Try it on your card!