Hi Kevin
Excel can only work with 15 digits, so your 16th value will always
change to 0 if you enter as numeric.
You need to enter it as Text (which Kassie's suggestion of including the
spaces would produce).
Alternatively, pre-format the column as Text then make your entries
(without the spaces if you wish) or type a single quote ' before
entering the number. This will make it a text entry, but the quote will
not show as part of the number.