Which is the main city in Mumbai?

Mumbai is the main city in the Mumbai Metropolitan Region (MMR), a metropolitan area in the state of Maharashtra, India. The MMR consists of Mumbai city and several suburbs and satellite towns that are economically and socially integrated with the city. Mumbai is the administrative capital of the state of Maharashtra, and is the most populous city in India with a population of over 21 million people. It is a major center of commerce, industry, and finance in India, and is also known for its rich cultural heritage, diverse population, and unique history.