We see it every time we write a check, but we don’t think much about it — the bank’s routing number. It is the first set of numbers at the bottom of every check you write.

A bank's routing number is a nine-digit number associated with a particular bank, while your account number is explicitly assigned to your account within a bank.

A bank’s routing transit number is located at the bottom of a check and is the first nine digits on the far left. The first four digits designate the Federal Reserve Bank of the district where ...