$6,472,200,000,000

But what if I do want to reduce the number of billionaires?

Well yes, but unless you dismantle things it'll probably backfire. A ton of that wealth is in owning companies, and if that ownership transfered to the state, it would need to be liquidated by selling it to... someone. Which would tank stocks, which would then tank 401ks and IRAs and a lot of other retirement funds, etc.. It would get messy and a ton of non-billionares would be impacted.

Now you can argue that you then use your newfound government cash to pay a new universal social security, and that's possible but you'd need to design all that ahead of time. Plus if your goal is to not impact people with less than a billion... well, no dice. It's hard to target just the billionaires, basically.

Still, if we could at least start the process that'd be lovely. Dismantling the whole system is more effective and way better, but my money would be on gradual socialist improvements paid via higher taxes and not a system overhaul. As it is, we're going backwards, though, so meh.

It'd be complicated to extract this from companies they own without destroying the companies. It could maybe work by force emmiting stock and the payments for it going directly to the government, so the company doesn't owe debt. The stock price will drop, so it will be affordable for workers to buy it and the former owner would basically be disowned at least partially.

The worst part is most of that money would end up right where it started.