One enormously successful career wasn’t enough for polymath James H. Simons. He became a world-class mathematician after earning his PhD. at age 23, joined the NSA as a codebreaker at age 26, won geometry’s top prize at 37, then founded a an extremely profitable hedge fund — Renaissance Technologies — at 44.

Jim Simons

Jim Simons: An unpretentious genius

Yet despite his impressive intellectual accomplishments and a net worth estimated at north of $12.5 billion, Jim Simons is described by his friends as “casual” and “unpretentious”.

Jim Simons is known as Jim to friends, family and colleagues, and his casualness belies an irrepressible intellect that seems to resonate with scientific minds.

“He’s an individual of enormous talent and accomplishment, yet he’s completely unpretentious,” said Marc Tessier-Lavigne, the neuroscientist president of Rockefeller University. “He manages to blend all these admirable qualities.”

It should not be implied that Jim Simons is without ego, however. On a wall in his office is a framed picture of the Chern-Simons equations, named after a paper he wrote 40 years ago with well-known mathematician Shiing-Shen Chern. Not surprisingly, the equations still define a number of aspects of modern physics, including theories of how invisible fields like those of gravity interact with matter to produce phenomena such as superstrings and black holes.

Still active in philanthropy and academia

Working closely with his wife, Marilyn, the president of the Simons Foundation and an economist credited with philanthropic savvy, Simons got serious about his philanthropic endeavors in 1994. Since then he has donated over $1 billion into a variety esoteric charitable and research projects. A couple of recent projects include the World Science Festival and an open to the public scientific lecture series hosted at his Fifth Avenue building.

The most recent Forbes magazine ranking listed Jim Simons as the world’s 93rd richest person, and in 2010, he and his wife were early signatories to the Giving Pledge promoted by Warren Buffett and Bill Gates, wherein wealthy individuals promise to give “the great majority” of their wealth to philanthropy.

A recent profile on Jim Simons in the New York Times recounts a recent conversation between Jim Simons and a colleague.

Bruce W. Stillman, director of the world-renowned Cold Spring Harbor Laboratory on Long Island, recalled noting a math journal on Simons’s desk and offering him a compliment on keeping up with his profession.

“He said, ‘What do you mean, reading?’ ” Dr. Stillman recounted. It turned out that issue of the journal contained a paper from Jim Simons. Noting that Simons is still active in business as well as philanthropy, Dr. Stillman added, “that’s pretty impressive.”