All mainstream credit card numbers obey a mathematical trick designed to catch the most common typos. It’s called the Luhn algorithm, named after IBM researcher Hans Peter Luhn, who patented it in ...

Your card number is carefully structured. The very first digit is what’s known as the major industry identifier. A 4 means ...

What Is the Luhn Algorithm? The Math Behind Credit Card Transactions Find out how this simple algorithm from the 1960s catches your typos ...