71% were Orthodox, 1% were Catholic, and 2% were Other Christians, while 15% were unaffiliated, 10% were Muslims, and 1% followed other religions. According to various reports, the proportion of Atheists in Russia is between 16% and 48% of the population. Islam is the second-largest religion in Russia, and it is the traditional religion amongst most peoples of the North Caucasus, and amongst some Turkic peoples scattered along the Volga-Ural region. Buddhists have a sizable population in three Siberian republics: Buryatia, Tuva, and Zabaykalsky Krai, and in Kalmykia, the only region in Europe where Buddhism is the most practised religion. Education Russia has an adult literacy rate of 100%. It grants free education to its citizens under its constitution. The Ministry of Education of Russia is responsible for primary and secondary education, as well as vocational education; while the Ministry of Education and Science of Russia is responsible for science and higher education. Regional authorities regulate education within their jurisdictions within the prevailing framework of federal laws. Russia is among the world's most educated countries, and has the third-highest proportion of tertiary-level graduates in terms of percentage of population, at 62%. It spent roughly 4.7% of its GDP on education in 2018. Russia has compulsory education for a duration of 11 years, exclusively for children aged 7 to 17–18. Its pre-school education system is highly developed and optional, some four-fifths of children aged 3 to 6 attend day nurseries or kindergartens. Primary school is compulsory for 11 year-olds, starting from age 6 to 7, and leads to a basic general education certificate. An additional two or three years of schooling are required for the secondary-level certificate, and some seven-eighths of Russians continue their education past this level. Admission to an institute of higher education is selective and highly competitive: first-degree courses usually take five years. The oldest and largest universities in Russia are Moscow State University and Saint Petersburg State University. There are ten highly prestigious federal universities across the country. Russia was the world's fifth-leading destination for international students in 2019, hosting roughly 300,000. Urbanized areas Russia is one of the world's most urbanized countries, with roughly 75% of its total population living in urban areas. Moscow, the capital and largest city, has a population estimated at 12.4 million residents within the city limits, while over 17 million residents in the urban area, and over 20 million residents in