The default or general numeric format of a cell is set to accept almost any number the user chooses to enter. Excel provides up to 15 significant digits, and the format options allow up to 30 decimal places. These numbers are available in Excel:

0.123456789123456 (15 significant digits)
0.000000000000000123456789123456 (15 significant digits, 30 d.p.)

But these are not:

0.1234567891234567 (16 significant digits)
0.0000000000000000123456789123456 (15 significant digits, 31 d.p.)

For integers there are 11 significant digits available before the display switches to scientific notation or standard format.

It is best to set the format of numbers to exactly what you require. Formatting options include currency, date, time, fraction and custom. Numbers can be set to the required format by selecting from the list of those available. Try entering some numbers into the spreadsheet (very large or very small ones if you wish) and then change their format.

Use the Back Button to Return to the previous page