This is a strange number, because apparently only 200,000 Jews survived the camps:
The exact number is unknown, and there are different definitions of Holocaust survivor.
“When the war ended on 8th May 1945, it is estimated that there were around 200,000 Jewish survivors of the forced labour camps, concentration camps, death camps and death marches. Thousands of other survivors, who had been with the partisan groups, or in hiding, were also freed from Nazi control. The majority of those who survived were aged between 16 and 40 years old. The death toll continued to rise after liberation, with tens of thousands dying of starvation, disease, and the after-effects of malnutrition.”
The Holocaust wiped out around two-thirds of the European Jewish population, or one third of the world Jewish population.
Source: Zoe Vania Waxman, Writing the Holocaust, Oxford University Press, 2006
Let’s compare that to WWII veterans:
Every day, memories of World War II—its sights and sounds, its terrors and triumphs—disappear. Yielding to the inalterable process of aging, the men and women who fought and won the great conflict are now in their late 80s and 90s. They are dying quickly—according to US Department of Veterans Affairs statistics, 389,292 of the 16 million Americans who served in World War II are alive in 2019.