The last column in Excel 2007 is XFD:
What number is that?
XFD =
X*26^2 + F*26^1 + D*26^0 =
24*26*26 + 6*26 + 4 =
16 224 + 156 + 4 =
16 384 = 2^14
So Excel uses 14 bits for columns which is odd, but I guess they use the other 2 bits for something else.
Also the base-26 numerical system (26 letters in English language) is pretty odd too, but I guess this is a legacy issue.
I would comment your idea about the "base-26 numerical system". When you try to define a cell in a matrix, it is better to use a letter and a number than two letters. It's easier to understand what C2 means than 3/2 or even better than 32. Just look at the chess notation for example.
So it has nothing to do with using base-x numerical system. It's usability 🙂