5. James Simons

It’s fitting that at this point in his life, James “Jim” Simons is counting on mathematics to make a difference in other people’s lives, thanks to his philanthropic support of the Math for America fellowship program, whose goal is that every student in America should learn the subject from an inspiring—and inspired—math teacher. Elected this year to the esteemed National Academy of Sciences, Simons knows that instilling a thorough understanding of math and science in the next generation is the key to helping our economy prosper. He’s taught math at M.I.T. and Harvard, and been the chairman of the math department at Stony Brook University. Certainly his affinity for numbers came in handy when Simons launched Renaissance Technologies LLC, a very successful hedge fund, where he was CEO until he retired in 2009, with an estimated net worth of $12.5 billion. Forbes currently ranks him No. 92 on their list of the top 100 of the world’s billionaires. Together with his wife, Marilyn, he manages the Simons Foundation, a charitable organization devoted to scientific research, which has launched a major initiative to understand the roots of autism, among other worthy causes.