You can format the cell to display a degree symbol with the number. This
will allow the numbers to be used in calculations:
Select the cells in which you will type the numbers
Choose Format>Cells
On the Number tab, choose Custom
In the text box, type: General
Then hold the Alt key, and on the number keypad, type 0176
Release the Alt key, and the degree symbol will appear.
General°
Click OK
If you want to use the symbol in a cell, and don't need the number to be
used in calculations, you can use Alt+0176 to add the symbol in the cell.