Midfirst Bank's routing number (the leftmost number on the bottom of a check) is 122187445. Sometimes, banks have multiple routing numbers for different branches or uses. Please make sure this is the correct routing number for your branch! The main phone number for Midfirst Bank is 405-717-3028. The assigned Federal Reserve Office for Midfirst Bank is Fed 121000374. A bank's Routing Transit Number (RTN) is a 9-digit code used to identify your bank on checks, direct deposit, bill pay, and in other transactions.