According to the 2011 census, the population of Mumbai was 12,478,447, According to extrapolations carried out by the World Gazetteer in 2010, Mumbai has a population of 13,830,884 and the Mumbai Metropolitan Area has a population of 21,347,412. The population density is estimated to be about 20,482. persons per square kilometre. As Per 2011 census, Greater Mumbai, the area under the administration of the BMC, has a literacy rate of 89.7 %, higher than the national average of 71.7%.
The sex ratio was 838 (females per 1,000 males) in the island city, 857 in the suburbs, and 848 as a whole in Greater Mumbai, all numbers lower than the national average of 914 females per 1,000 males. The low sex ratio is due to a large number of male migrants who come to the city to work.
Residents of Mumbai call themselves Mumbaikar, Mumbaiite or Bombayite. Mumbai has a large polyglot population like any other metropolitan city of India. Marathi, the official language of Maharashtra state, of which Mumbai is the capital, is widely spoken and understood in the city. Sixteen major languages of India are also spoken in Mumbai, most common being Marathi, Hindi, Gujarati and English. English is extensively spoken and is the principal language of the city's white collar workforce. A colloquial form of Hindi, known asBambaiya — a blend of Marathi, Hindi, Indian English and some invented words — is spoken on the streets.
Mumbai suffers from the same major urbanisation problems seen in many fast growing cities in developing countries: widespread poverty and unemployment, poor public health and poor civic and educational standards for a large section of the population. With available space at a premium, Mumbai residents often reside in cramped, relatively expensive housing, usually far from workplaces, and therefore requiring long commutes on crowded mass transit, or clogged roadways. Many of them live in close proximity to bus or train stations although suburban residents spend significant time travelling southward to the main commercial district. Dharavi, Asia's second largest slum is located in central Mumbai and houses 800,000 people. With a literacy rate of 69%, the slums in Mumbai are the most literate in India.
The number of migrants to Mumbai from outside Maharashtra during the 1991–2001 decade was 1.12 million, which amounted to 54.8% of the net addition to the population of Mumbai.
The religions represented in Mumbai include Hindus (67.39%), Muslims (18.56%), Buddhists (5.22%), Jains (3.99%), Christians (4.2%),Sikhs (0.58%), with Parsis and Jews making up the rest of the population. The linguistic/ethnic demographics are: Maharashtrians (42%), Gujaratis (19%), with the rest hailing from other parts of India. The oldest Muslim communities in Mumbai include the Dawoodi Bohras, Khojas, and Konkani Muslims.Native Christians include East Indians (ethnic group) Catholics who were converted by the Portuguese, during the 16th century. The city also has a small native Bene Israeli Jewish community, who migrated from the Persian Gulf or Yemen, probably 1600 years ago. Mumbai is also home to the largest population of Parsi Zoroastrians in the world, with about 80,000 Parsis in Mumbai. Parsis migrated to India from Pars(Persia/Iran) following the Islamic conquest of Iran in the 7th century AD.