According to a post on the Microsoft Developer Network's Excel blog, the spreadsheet application gives erroneous results for 12 basic multiplication operations that a pocket calculator could handle flawlessly. Those operations include 7.1*850, 5.1*12850, 10.2*6425, 20.4*3212.5, and a few others that add up to either 65,535 or 65,536. In those cases, Excel erroneously returns a result of 100,000:

Yesterday evening we were alerted to an issue in Excel 2007 (and Excel Services 2007) involving calculation of numbers around 65,535. The first example that we heard about was =77.1*850, but it became clear from our testing as well as additional reports that this was just one instance where Excel 2007 would return a value of 100,000 instead of 65,535. The majority of these additional reports were focused on multiplication (ex. =5.1*12850; =10.2*6425; =20.4*3212.5 ), but our testing showed that this really didn't have anything do to with multiplication - it manifested itself with many but not all calculations in Excel that should have resulted in 65,535 (=65535*1 and =16383.75*4 worked for instance). Further testing showed a similar phenomenon with 65,536 as well. This issue only exists in Excel 2007, not previous versions.