<diacritize> By 2015 , Mumbai formerly called Bombay is expected to have 22.6 million inhabitants , Delhi 20.9 million , Mexico City 20.6 million , and Sao Paulo 20 million . <yor>By 2015 , Mumbai formerly called Bombay is expected to have 22.6 million inhabitants , Delhi 20.9 million , Mexico City 20.6 million , and São Paulo 20 million . 