Rio de Janeiro
Rio has more people living in slums than any other city in Brazil, according to the 2010 Census. More than 1,500,000 people live in its 763 favelas, 22% of Rio's total population. São Paulo, the largest city in Brazil, has more favelas (1,020) in sheer numbers, but proportionally has fewer people living in favelas than Rio.
Telephone numbers in Brazil
However, the popularity of multiple-SIM mobile phones in Brazil makes the country have more active mobile lines than inhabitants (as of November 2016, 248 million vs. 206 million), and by 2010 the country's most populous and economically important area code, "11" of metropolitan São Paulo (an area where over 20 million people live), was getting close to exhausting its available mobile numbers. Overlays and extra area codes were considered, but deemed confusing and impractical for local conditions.