His father Mark having been a merchant, Alexander Ostrowski attended the Kiev College of Commerce, not a high school, and thus had an insufficient qualification to be admitted to university. However, his extraordinary talent did not remain undetected: Ostrowski's mentor Grave wrote to Landau and Hensel for help.
Subsequently Ostrowski began to study mathematics at Marburg University under Hensel's supervision in 1912.
After World War I had ended Ostrowski moved on to Göttingen where he wrote his doctoral dissertation and was influenced by Hilbert, Klein and Landau.
In 1920, after having obtained his doctorate, Ostrowski moved to Hamburg where he worked as Hecke's assistant and finished his habilitation in 1922.
