According to the census survey carried out between 15 June and 31 July 2004, Montevideo had a population of 1,325,968 persons, compared to Uruguay's total population of 3,241,003. The female population was 707,697 (53.4%) while the male population accounted for 618,271 (46.6%). The population had declined since the previous census carried out in 1996, with an average annual growth rate of −1.5 per thousand. Continual decline has been documented since the census period of 1975–1985, which showed a rate of −5.6 per thousand. The decrease is due in large part to lowered fertility, partly offset by mortality, and to a smaller degree in migration. The birth rate declined by 19% from 1996 (17 per thousand) to 2004 (13.8 per thousand). Similarly, the total fertility rate (TFR) declined from 2.24 in 1996 to 1.79 in 2004. However, mortality continued to fall with life expectancy at birth for both sexes increasing by 1.73 years.

According to the census survey carried out between 15 June and 31 July 2004, what was Montevideo's population?