A perfect number is a number which is equal to the sum of its factors, including 1 (but not the number itself).

This page is an exercise using web workers to perform calculations in the background.

It takes a fraction of a second to find the first 4 perfect numbers, and roughly 8 mins to find the 5th (depending on browser, processor speed, etc); the script has yet to come up with the 6th perfect number despite exciting millions of electrons for well over an hour.