Could I predict rises and falls in the stock market? Make loads of money in investment? Work out a mathematical theorem that allows me to sleep with exactly 22 women every day (I’ve got it down to 18 - boy my life’s work is sooooo hard)…

Come on… pull out all the stops… be imaginative (but try to stick to the subject matter)… So, what could I (or you) do if I (or you) were the greatest ever mathematical being?

Graham’s Constant, or something like that … I don’t remember precisely what it was. ultrafilter, he of the thread detailing it, might be able to clue you in more adequately;)

Your could call yourself a “Mathemagician” and get a wizards’ cloak and peaked hat with numbers and formulas all over it. IIRC I think this is how cabbage dresses.

Let’s look at some past famous mathematicians (I’ll include physicists):

Newton: probably died a virgin.
Gauss: Killed young in a duel over a woman, which was probably a goverment assassination.
Stephen Hawking: …
Andew Wiles: the nearest thing to fame any of get nowadays…

OTOH, if you forgo true mathematics, you might well be able to make a killing on the stock market. But no-one’s going to call you the bets mathematician of all time.

You could derive great enjoyment fiddling with patterns nobody else can see. I think that’s about it, but there are worse ways to spend your time. The downside is that if someone finds something practical to do with anything you’ve come up with, it’ll probably be a weapon.

This list is a little unfair. I believe Euler had huge numbers of children, Gauss lived to a ripe old age (and left a large estate behind), and Newton chose to be a virgin. Otherwise, Newton did take advantage of his “fame”. A better list would be

Galois: died young in a ditch after being shot in a duel
Abel: died young and in extreme poverty, with no one realizing his genius until afterwards
Riemann: died young
Archimedes: died old, but at the hands of a Roman soldier he pissed off.

To answer the OP, if I were tgreatest mathematician I could predict how many women I could pick up at the bars: zero.

I might earn a few million bucks solving the greatest outstanding math problems, though.

Forgot to add, if you were the world’s greatest mathematician, or any kind of mathematician at all, you would learn quickly how bad at math everyone around you is. It’s completely mystifying, but for some reason people seem to feel the need to confess to us.