I spent most of my full life (birth to death) in Braunschweig, Gedrmany.
At the University of Göttingen, I studied number theory under Moritz Stern and was the last student of Gauss.
Eventually, I became a lecturer at Göttingen in the areas of probability and geometry, even though my primary interest was in number theory...and became a great friend of Dirichlet.
As the first Göttingen person to give lectures on Galois theory, some claim I was the first mathematician to understand the fundamental importance of the notion of groups for algebra and arithmetic.
One claim to fame is my development of the idea of a "cut," which is still used to define the real numbers.
While on a holiday, I met Georg Cantor, became his friend, admired his groundbreaking work on infinite sets, and supported him in his battles with Kronecker, who philosophically rejected the idea of transfinite numbers.
Answer:
Julius Wilhelm Richard Dedekind (1831  1916)
