Luxembourg is a constitutional monarchy governed under the constitution of 1868 as revised. The hereditary monarch, the titular head of state, has a largely ceremonial role. The government is headed by the prime minister, who is appointed by the monarch with the approval of the legislature. The 60 members of the unicameral legislature, the Chamber of Deputies, are elected by popular vote to five-year terms. The 21 members of the Council of State, an advisory body to the legislature, are appointed by the monarch on the advice of the prime minister. Administratively the country is divided into three districts.