Born in Shavli[1][2] (then Imperial Russia, now Lithuania) into the family of Shmuel Dantzig (?-1940) and Guta Dimant (1863–1917), he grew up in Lodz and studied mathematics with Henri Poincaré in Paris.[3] His brother Jacob (1891-1942) was murdered by the Nazis during the Holocaust; he also had a brother Naftali (who lived in Moscow) and sister Emma.