The number given (1,606,748) represents only a small fraction of the people killed by Stalin. A lot of people lost their lives in the purges and famines.
USSR population
January 1926 : 148,656,000
January 1937: 162,500,000
January 1939: 168,524,000
June 1941: 196,716,000
January 1946: 170,548,000
January 1951: 182,321,000
According to the British historian Norman Davies, some 50 million people lost their lives during 1924-53 (excluding deaths due to warfare). Some 5 million lost their lives during the famine of 1930–1933 alone, which was a result of Stalin's incompetence.
Losing the million of lives would create demographic hole which is impossible to hide because such hole will persist for a dozen of generations. There are irrefutable traces of 1941-1945 deaths in Belarus, Ukraine and Russia. But there are no demographic holes matching to the interval of 1930-1934, for example. I don't care what Norman Davies have said because it's simply impossible. It's not a history, but simple arithmetics.
P.S. Demographic hole is specified as a significant drop of newborns with a period of 20-22 years. It's like an echo of the past.