Signature Bank's routing number (the leftmost number on the bottom of a check) is 91017581. 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 Signature Bank is 952-746-3384. The assigned Federal Reserve Office for Signature Bank is Fed 091000080. 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.