The sets of numbers typically included on a personal check are the routing number, the account number and the check number, explains The Nest. The first number, the routing number, is always nine digits in length.
According to The Nest, a routing number identifies the bank at which the account is held. The second set of numbers identifies the check owner's checking account number. The third, shorter set of numbers is the check number and is typically only four digits in length. This number is used by the check's owner and the bank to track the check, and it corresponds to the check number on the upper-right corner of the check.
RoutingNumbers.org explains that bank routing numbers, also called routing transit numbers (RTN), are used to identify financial institutions, and some banks or credit unions may have multiple routing numbers for different purposes. Most financial institutions publish routing numbers on the company website.