Passage: The 1931 China floods, or the 1931 Yangtze–Huai River floods, were a series of devastating floods that occurred in the Republic of China. They were some of the deadliest floods in history, and together formed one of the most lethal natural disasters of the 20th century, excluding pandemics and famines. Estimates of the total death toll range from 422,499 to between 3.7 million and 4 million.

Question: What is the estimate of the number of deaths?
422,499 to between 3.7 million and 4 million.