All mainstream credit card numbers obey a mathematical trick designed to catch the most common typos. It’s called the Luhn ...

The Luhn algorithm—also known as the “Modulus 10 algorithm”—is a formula used to determine the accuracy of credit card numbers.

Credit card numbers aren't random, and they don't only identify your account. Here's how to decipher what your own credit card number means.

The Luhn algorithm uses modulo-10 mathematics. To calculate the check digit, multiply every even-position digit (when counted from the right) in the number by two.