Excel only keeps track of 15 significant digits.

If you can treat the entry as text, then

you can preformat the cell as Text, then do the data entry
or
you can start your entry with an apostrophe: '1234123412341234



Donald T wrote:

When I enter a 16 digit number on a 2004 excel for Mac spread sheet, the l6th
digit changes to 0 no matter what it was that I typed.

I can enter a 15 digit number with no changes.

--

Dave Peterson