What remains (sans the final digit) is your specific account number within that bank. The final digit, sometimes called the “check digit,” has nothing to do with financial institutions. Issuers tack ...

Katie has a PhD in maths, specializing in the intersection of dynamical systems and number theory. She reports on topics from maths and history to society and animals. Katie has a PhD in maths, ...

Here’s a fun trick to entertain friends and win bar bets: Guess the first number on somebody’s credit card tucked away in their wallet. You can do that because credit card numbers aren’t random. Using ...