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Alexander Grothendieck was born on March 28, 1928.
Alexander Grothendieck was 86 years old when he died on November 13, 2014 (birthdate: March 28, 1928).
Hes still alive
This is a really naive and stupid question. There is nothing more to say at this place.
(And by the way, Grothendieck is written with a capital "G", and he usually calls himself "Alexandre", not "Alexander".)