I subscribe to a site called Cantor's Paradise, which includes interesting stories about different facets of mathematics.
A famous mathematician, and subject of a book or two, is Srinivasa Ramanujan. His contributions are legion. Well, here is something that I didn't know about him. He proved that
1 + 2 + 3 + ⋯ + ∞ = -1/12
Yep. The sum of the integers through infinity equals -1/12. Turns out to be an important result, especially for quantum mechanics and string theory.
A short and very accessible article can be found here:
https://medium.com/cantors-paradise/...2-a8cc23dea793
Math is weird.