Excel supports 15 digits of precision in its cells. Credit card numbers are usually 16 digits. When you enter a number greater than 15 digits, Excel rounds it off and you get zeros padding the end of your number. Enter the number
in Excel and you get this
If you have a large number like this that’s causing a problem in Excel, there’s usually one of two reasons: You are an astrophysicist and you shouldn’t be using Excel to do your calculations; or the number your using is an identifying number, that is, you won’t be doing any math with it.
For identifying numbers, you should enter them as text. To enter a number as text, precede the entry with an apostrophe (‘) or format the cell as Text (Format>Cells>Number) before you enter the number.