According to Check Advantage, bank account numbers differ from bank to bank. A bank account number can contain up to 18 digits. The bank account number is located at the bottom of the check, immediately following the routing number, which identifies the bank within the financial system.
Check Advantage explains that a bank account number is used to set up direct deposit, to order additional checks or to set up automatic bill payment from a checking account. The bank account number is also needed to complete a wire transfer from one bank to another. Some bank account numbers include spacing between the numbers.