Third new Wikipedia Good Article of the month: Euclid–Euler theorem, https://en.wikipedia.org/wiki/Euclid%E2%80%93Euler_theorem

It's about the 2-millenium-long collab in which Euclid proved that all Mersenne primes produce even perfect numbers, and Euler proved that all even perfect numbers come from Mersenne primes. But let's not forget Ibn al-Haytham (https://en.wikipedia.org/wiki/Ibn_al-Haytham, Alhazen), halfway between them in time, who conjectured Euler's result but couldn't prove it.