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t *you*, the viewers, to join in! Make your own video about your favourite mega-number. You can think of a cool big number, or think of a cool topic first and hang a mega-number on it. Upload your videos to YouTube with the hashtag #MegaFavNumbers and with MegaFavNumbers in the title, and your video will be added to the megafavnumbers playlist. Submit your videos anytime before Wednesday 2nd September to be added to the MegaFavNumbers playlist! MegaFavNumbers Playlist: https://www.youtube.com/playlist?list=PLar4u0v66vIodqt3KSZPsYyuULD5meoAo Amicable Numbers on Wikipedia: https://en.wikipedia.org/wiki/Amicable_numbers Here is a list of amicable numbers: http://www.vaxasoftware.com/doc_eduen/mat/numamigos_eng.pdf A list of sums of amicable numbers https://oeis.org/A180164 Remember, a test for divisibility by 9 is to add all the digits of the number together, and to do the same with the result, until you get a single digit. If the end result is 9 then the original number was a multiple of 9. Here is a list of even amicable numbers whose sum is not divisible by 9 https://oeis.org/A291550 And here are those complicated mathematical conditions https://www.ams.org/journals/mcom/1969-23-107/S0025-5718-1969-0248074-6/S0025-5718-1969-0248074-6.pdf