This article investigates the fin- and finger-number dependence of the total ionizing dose (TID) degradation in 16-nm bulk Si FinFETs at ultrahigh doses. n- and p-FinFETs designed with different numbers of fins and fingers are irradiated up to 500 Mrad(SiO2) and then annealed for 24 h at 100 degrees C. The TID responses of nFinFETs are insensitive to the fin number, as dominated by border and interface trap generation in shallow trench isolation (STI) and/or gate oxide. However, pFinFETs show a visible fin-number dependence with worst tolerance of transistors with the smallest number of fins. The fin number dependence may be related to a larger charge trapping in STI located at the opposite lateral sides of the first and last fins. In addition, both n- and p-FinFETs exhibit an almost TID insensitivity to the finger number. During the design of integrated circuits, the TID tolerance of electronic systems can be enhanced by preferably using transistors with a higher number of fins than fingers.