I work for a charity. We have an agency which collects new donors for us. On
a weekly basis, this agency sends me a spreadsheet file containing data about
the new donors which I import into our database.

One item of data they collect is credit card numbers as credit cards are
used to pay donations. Unfortunately, given that Mastercard and Visa card
numbers are 16 digits long, the credit card data we get back from the agency
always has the last value (the 16th number) as a zero. I am assuming that
Excel is accurate to 15 digits only. This means that, 9 out of 10 times, I
have to manually change the last digit in the database after it has been
imported from Excel.

Is there any way to get Excel to show a 16 digit number correctly and/or is
it possible to display a 16 digit number in 4 blocks of 4 as in 1234 1234
1234 1234 (preferably).