Numbers in Excel

How are numbers stored, formatted and calculated? When dealing with numbers in Excel we should be aware of a few things: numbers in Excel can be formatted in many ways: plain numbers, currency, percentage, date etc. no matter how they are formatted and possibly edited, underlying values saved in cells are still decimal numbers those decimal numbers that Excel uses and calculates with go up to 15 decimal places (and even with that, there are caveats) this is not changed