[webglfan]

I'll give you one: "Do any odd perfect numbers exist?"

You can read about it here: https://en.wikipedia.org/wiki/Perfect_number#Odd_perfect_num...

You can watch a short documentary about it here: https://www.youtube.com/watch?v=Zrv1EDIqHkY

[gnatman]

Wonderful quote in there from James Joseph Sylvester:

>>... a prolonged meditation on the subject has satisfied me that the existence of any one such [odd perfect number] —its escape, so to say, from the complex web of conditions which hem it in on all sides— would be little short of a miracle.

[brihati]

Is 2+2 still 4 :p