Excel has a 15 significant-digit limit.

Precede the numbers with an apostrophe to enter as text or pre-format the
cells as Text before entry.

Gord Dibben Excel MVP

On Wed, 8 Dec 2004 11:03:03 -0800, "OldManP"
wrote:

I read that Excel displays rounded numbers, though the actual values will
remain the same for calculations. I'm trying to simply input a credit card
number (16 digits), and it keeps rounding the last digit down to zero. I
can't figure out how to stop this from happening. Any one else know how to
prevent this?