“I’d swap all my wealth for a healthy 21-year-old self tomorrow. But I can’t find any 21-year-olds who want to swap with me.”

Clearly, Sir Richard Branson jests, as we can’t imagine anyone of any age who wouldn’t trade places with the megabiz-founding, balloon-flying, eco-warrioring billionaire turned humanitarian.

Right now the Virgin Group founder’s armada of companies is seeking solutions for global warming; orbiting 2,000-plus satellites so 4 billion cyberless folks can go online; supplying electricity and solar power to Africa; and spearheading clean-water initiatives.

“We’re also working on flying cars,” he says.

His most recent quest: making exercise fun with “festivals of fitness” (run by his new Virgin Sport) that bring people together for workout challenges.

And he’s not just the owner, he’s also a client: “Life’s gonna be a hell of a lot more rewarding,” he says, “if I can get my body back to what it was when I was in my 20s.”