Each type of account number has specific lengths, which can serve as a secondary method to identify the type of credit card. For example, Visa account numbers can be up to 19 digits.

Why do computers only work with the numbers 0 and 1? There are machines that process three digits with more efficiency than ...

A routing transit number (RTN) is a unique nine-digit numerical code used to identify a physical bank, digital bank, or other financial institution.

Vanity numbers are used by big companies and individual entrepreneurs. Nov. 7, 2011— -- For some, the 10-digit code others use to call them isn't just a phone number -- it carries a personal ...