Write a question about the following article: The German government led by Adolf Hitler and the Nazi Party was responsible for the Holocaust , as well as for killing of 2.7 million ethnic Poles, and 4 million others who were deemed "unworthy of life"  as part of a programme of deliberate extermination. Soviet POWs were kept in especially unbearable condition, and, although their extermination was not an official goal, 3.6 million of Soviet POWs out of 5.7 died in Nazi camps during the war. In addition to concentration camps, death camps were created in Nazi Germany to exterminate people at an industrial scale.Nazi Germany extensively used forced labourers. About 12 million  Europeans from German occupied countries were used as slave work force in German agriculture and war economy. Soviet Gulag became de facto a system of deadly camps during 1942-43, when wartime privation and hunger caused numerous deaths of inmates, including foreign citizens of Poland and other countries occupied in 1939-40 by the USSR, as well as of the Axis POWs.By the end of the war, most Soviet POWs liberated from Nazi camps and many repatriated civilians were detained in special filtration camps where they were subjected to NKVD check, and significant part of them was sent to Gulag as real or perceived Nazi collaborators.

Question about the article:
How many million Soviet POWssurvived the Nazi camps?