### Instruction: How many cities in the world have a population exceeding 5 million people ?
### Input: There are 81 cities in the world with a population exceeding 5 million people.
### Response: There are 81 cities in the world with a population exceeding 5 million people, according to 2018 estimates by the United Nations. The U.N. figures include a mixture of city proper, metropolitan area, and urban area.