Don't feel bad boins, that is certainly in contention for the most useless skill ever. This link claims in fact that knowing 41 digits of pi is enough to calculate a circle that is the circumference of the known universe. So 40 is probably overkill for any real world application.
It's honestly not remarkably hard. I memorized the amount I know one night sophomore year of high school when I liked a guy that was into that kind of thing. It's just stuck in there since, but especially if you're looking to know something to show off (as all good idols should be), it's a generally impressive thing that appeals to the wota nerds, y'know?
Earlobe trick girl definitely trumps the hell out of this, though.