First thing is: Don't expect to get that money back!
I'd buy a lot of things, or use familyfunds to reduce your money. Point is, even though your sims are rich, you're not really going to be able to do much. I mean, sure there is no point making money when you have $78million, but when you've hit the cap, the money literally vanishes.
Another idea is to invest. That money will come back, but over a moderate period of time.
Donate to "charity". E.G. The Alvi family live with little to no money (even though they're probably dead because you're on Week 30, I read on another thread).
Use FamilyFunds to reduce your money by, say, $10,000,000 and then use FamilyFunds to give the Alvi family $10,000,000.
But great job on managing to earn that amount of money!