This page runs a script that will return the prime factorization of a positive integer. Of course the bigger the number, the longer it will take. Just to be safe I decided to limit it to numbers less than 1,000,000 (see below). Even with this limit, some numbers (those with very large prime factors) may take a few minutes to factor if your computer has a slow processor, so be patient if nothing happens after you click the button.
Question: Try factoring 39929. What happens? What does that tell you? Answer
*You can override this limit by checking the box, but be careful about putting in really big numbers. Depending on your browser, there will be a limit to just how big an integer it can handle before it blows a gasket (Windows95 doesn't seem to like integers with more than 9 digits). In order for this factoring to work, the computer must retain all the digits of the number with no roundoff. If you put in too large a number the script probably won't recognize it as an integer and will reject it, but there is a chance that your computer may appear to hang up, or you may get a warning from your browser that the script is taking a very long time. You may ignore this warning and it will keep working, but if you get tired of waiting you may have to reboot your computer (try ctrl-alt-delete; if that doesn't work just turn off the computer—if that doesn't work, call an exorcist).