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 ...

Jason Fernando is a professional investor and writer who enjoys tackling and communicating complex business and financial problems. Khadija Khartit is a strategy, investment, and funding expert, and ...

You’re at the checkout screen after an online shopping spree, ready to enter your credit card number. You type it in and instantly see a red error message ...

Most of us carry credit cards and ATM cards. These, typically, have sixteen digits on the front. These digits are the unique account number for the card. For obvious reasons, just any sixteen digits ...