Is it possible to position a PAGE NUMBER on the side of a sheet? If
so, can I position it sideways. My sheet is landscape and I want the
page # to be position on the left side horizontally.

You might think this silly, but instead of rotating the page number you
could make all the cells of the sheet sideways using
Format Cells Alignment Orientation
and rotating 90 degrees.

Then the header/footer would be perpendicular to the data.

One reason it's silly is it makes the data harder to work with. Still, the
appearance is what you want.