Kleitman was born in 1934 in
Brooklyn,
New York, and he graduated from
Morristown High School in 1950. He is the "k" in
G. W. Peck, a pseudonym for a group of six mathematicians that includes Kleitman. Formerly a physics professor at
Brandeis University, Kleitman coauthored at least six papers with Erdős, giving him an
Erdős number of 1. He was a math advisor and extra for the film
Good Will Hunting. Since
Minnie Driver, who appeared in
Good Will Hunting, also appeared in
Sleepers with
Kevin Bacon, Kleitman has a
Bacon number of 2. Adding the two numbers results in an
Erdős–Bacon number of 3, which is a tie with
Bruce Reznick for the lowest number anyone has. In 1973 Kleitman was elected as a member of the
American Academy of Arts and Sciences. In 2024 Kleitman was elected as a member of the
National Academy of Sciences. ==Personal life==