Eliezer Ehrenpreis was a multitasker.
The mathematics professor told Temple University's Temple Times in 2002 that he trained for New York City Marathons by running on the Coney Island beach, near his Brooklyn home.
"I do mathematics problems in my head, but only while training," he said. "During the race you have other things to concentrate on."
He had entered every New York Marathon since the first in 1970. When he was 77, he ran his last in 2007.
On Aug. 16, Dr. Ehrenpreis, 80, known as Leon, an Orthodox rabbi who had been a Temple mathematics professor since 1984, died of heart failure at Memorial Sloan-Kettering Cancer Center in New York.
A daughter, Yael Meyer, said his weakened heart had resulted from chemotherapy for prostate cancer.
Israel National News reported that Dr. Ehrenpreis was "an eminent scholar of Talmudic texts who received rabbinical ordination from the greatest [authority] of Jewish law in the post-Holocaust period, Rabbi Moshe Feinstein."
And he shared, with Bernard Malgrange of France, authorship of the Malgrange-Ehrenpreis theorem, which might be more puzzling for a layman to understand than it was for the two, working independently in their two countries, to solve.
The theorem "states that for a certain very large category of partial differential equations, there is a solution," said Temple mathematics professor Marvin Knopp, a close friend. ..But the solution requires more math than the Phillies' won-lost record.
"Without an understanding of the theory of partial differential equations," Knopp said, "our modern technological society would not be possible."
"This is a very, very big deal," he added, and Mr. Ehrenpreis solved it in his early 20s. "He was an enormous international figure in the mathematics community. He was invited everywhere."
Knopp first met Dr. Ehrenpreis when they were doing summer work at the Hebrew University of Jerusalem. Dr. Ehrenpreis was also a visiting professor at the University of Paris and at Kyoto University in Japan. Year after year he commuted daily between Brooklyn and Temple, his daughter said. "Most of the years, he taught two days a week," Meyer said. "In recent years, in certain semesters, he taught three or four days a week."
Even this year, when he turned 80 in May, he took the Q subway to Manhattan and then an Amtrak train to Philadelphia, she said.
"He always said a train is a good place to get work done."
An early bloomer in mathematics, Dr. Ehrenpreis was a late bloomer in running, at 38. When he ran the inaugural New York City Marathon, his first marathon, he was 40.
His best finish - 3 hours and 10 minutes - happened in 1972, but in later years the race was a six-hour experiment in excruciating endurance. "The marathon was like the Ehrenpreis Family Holiday," Meyer said. "We would all stand at the same spot in Central Park every year so that my father would know where to look for us, and then afterward we would all get together and celebrate."
Dr. Ehrenpreis was born in Brooklyn and earned all his degrees in mathematics: a bachelor's at City College of New York in 1950, a master's in 1951 at Columbia University, and a doctorate there in 1953.
During the Korean War, he was a member of the New York Army National Guard.
He was an associate professor of mathematics at Brandeis University from 1957 to 1969 and held the same position at Yeshiva University in New York from 1959 to 1961.
In 1961-62, he was one of 59 members of the School of Mathematics at the Institute for Advanced Study in Princeton.
He returned to teaching from 1962 to 1968 as a professor at the Courant Institute of Mathematical Sciences, part of New York University.
And he returned to Yeshiva as professor of mathematics from 1968 to 1984 before joining the Temple faculty.
Besides a just-completed work of biblical scholarship and other published mathematical works, he wrote two textbooks, Fourier Analysis in Several Complex Variables (1970) and The Universality of the Radon Transform (2003).
Besides Meyer, Dr. Ehrenpreis is survived by his wife, Ahava; sons Akiva, Raphael, and Saadya; daughters Ann Scherzer, Kiki Beth Ehrenpreis, Naomi Voss, and Yocheved Orlofsky; a brother; and 13 grandchildren. A funeral took place Aug. 17 at Shomrei Hachomos chapel in Brooklyn.