R. D. (Robert Daniel) Carmichael

Born in Goodwater, Alabama, in 1879, he studied at Lineville College and later completed a Ph.D. in mathematics at Princeton in 1911 under G. D. Birkhoff. Before that, he had trained as a Presbyterian minister and had already built a remarkable record of publishing mathematical problems and papers.

He is remembered above all for discovering what are now called Carmichael numbers in 1909, a contribution that kept his name firmly attached to number theory. He also worked on difference equations and other areas of mathematics, and his career included teaching posts at Indiana University and the University of Illinois.

Carmichael died in 1967, but his work still appears in the language of modern mathematics through terms such as Carmichael numbers and the Carmichael function. He stands out as one of those scholars whose ideas remained useful long after his own era.