I noticed today that Excel does not allow more than 15 digits in a cell. If you a type a number with more than 15 digits into an excel cell, the digits after the first 15 get replaced by zeroes. I had a hard time trying to figure out how to fix this. You can make the cell accept more than 15 digits by:
 pre-formatting the cells as text fields BEFORE pasting the values
 by start the number with an apostrophe i.e. ‘
From Microsoft Knowledge Base 269370:
Excel follows the IEEE 754 specification on how to store and calculate floating-point numbers. Excel therefore stores only 15 significant digits in a number, and changes digits after the fifteenth place to zeroes.
To work around this behavior, format the cell as text. The cell can then display up to 1,024 characters.”