Off topic (because the topic is about very big and very small numbers, and I think it's mind boggling):
1 + 2 + 3 + 4 + 5 + ... = -1/121
Only if you use a very specific treatment of infinity that also happens to be useful in physics (edit: or was it quantum mechanics.. hmmm, already forgot) because it actually ends up matching what they're seeing 1 + 2 + 3 + 4 + 5 + ... = -1/121
( saw that vid a while back - there's all sorts of mathematical oddities in those channels, well worth subscribing. )
In one of the videos it was mentioned that it appears in the beginning of quantum mechanics books. It is one of the reasons why the number of dimensions is what it is in string theory, because of that outcome.
I want to make a remark that pure mathematically it can be deduced from the Riemann zeta function. So maybe they found it because of physics, but it also exists in the abstract world of mathematics.