Ernst Erich Jacobsthal (16 October 1882, Berlin – 6 February 1965, Überlingen) was a German mathematician, and brother to the archaeologist Paul Jacobsthal.
In 1906, he earned his PhD at the University of Berlin, where he was a student of Georg Frobenius, Hermann Schwarz and Issai Schur; his dissertation, Anwendung einer Formel aus der Theorie der quadratischen Reste (Application of a Formula from the Theory of Quadratic Remainders), provided a proof that prime numbers of the form 4n + 1 are the sum of two square numbers.
- ^ a b Selberg, Sigmund (2006-10-27). "Ernst Jacobsthal" (in English and translated from Norwegian). Retrieved 2007-10-05.
- ^ "Ernst Jacobsthal". Mathematics Genealogy Project. Retrieved 2007-10-05.