More than half of member states—15 out of 27—are parliamentary republics, while six states are constitutional monarchies, meaning they have a monarch although political powers are exercised by elected politicians. Most republics and all the monarchies operate a parliamentary system whereby the head of state (president or monarch) has a largely ceremonial role with reserve powers. That means most power is in the hands of what is called in most of those countries the prime minister, who is accountable to the national parliament. Of the remaining republics, five operate a semi-presidential system, where competencies are shared between the president and prime minister, while one republic operates a presidential system, where the president is head of state and government.