What is lanzhou population?

As an AI language model, I don't have access to the real-time data, but according to the statistics from the Chinese government in 2020, the population of Lanzhou was approximately 4.05 million, which ranked as the 15th most populous city in China. Lanzhou is the capital and largest city of Gansu Province in Northwest China, situated on the banks of the Yellow River. The population of Lanzhou has been steadily increasing due to the city's economic growth, migration, and urbanization.