Your numbers are probably seen as text, make sure there is no alignment in
the cells, the default for text is left aligned so if your numbers are left
aligned they are text, did you import them (that is a often a problem with
numbers seen as text)?

You can try to convert them to text, make sure the format in the cells are
general, then select the range with numbers and do data>text to columns,
then click finish, now try it