The world's first trillionaire, Elon Musk, said it's "not impossible" for him to become the world's first quadrillionaire. An X user noted that Musk needs $998.9 trillion to become humanity's first quadrillionaire, to which Musk responded, "Definitely requires factories on Moon and Mars to achieve [quadrillionaire status]." "By then, I don't think dollars will be used as currency," Musk added.