From Wikipedia:
The city has a population of 1,399,519 (the municipality, 1,485,941).[citation needed] The metropolitan area of the city, however, extends over 10 municipalities of the state of Puebla, such as the city of Cholula and 13 of the state of Tlaxcala, and with a population of 2,109,049 it is fourth most populous metropolitan area in Mexico.