New Delhi, June 13 -- In a post on the social media platform he owns, Elon Musk recently said, "Whoever said 'money can't buy happiness' really knew what they were talking about."

Already the wealthiest person on the planet, Musk can now add another distinction to his belt-the world's first trillionaire.

Shares of SpaceX rose 19% Friday to $160.95 each in their first day of trading, vaulting the value of the rocket and AI company Musk founded to $2.2 trillion. His fortune now stands at the once-unimaginable figure of $1.1 trillion, according to the Bloomberg Billionaires Index. That's more than three times that of the world's second-richest person, Google co-founder Larry Page.

Less than a decade ago, crossing the $100 billion wealth m...