If it is a formula then you might be able to do what I suggested, as part of the formula in the same cell.
If you are typing these numbers in, when you get to that digit, use Command Control Shift + to make it a superscript then type the digit. Just remember that it will make the number a text "number". The numeric functions will ignore it but +-*/ will accept it as a number. In a separate column you can multiple it by 1 to make it an actual number if you need to.
If you are doing this a lot and Command Control Shift + is a bit much to type, you can redefine the keyboard shortcut to something easier in System Preferences->Keyboard Shortcuts->App Shortcuts.