to nongovernmental organizations; as of April 2021, close to 5,600 organizations have this status. Specialized agencies The UN Charter stipulates that each primary organ of the United Nations can establish various specialized agencies to fulfil its duties. Specialized agencies are autonomous organizations working with the United Nations and each other through the co-ordinating machinery of the Economic and Social Council. Each was integrated into the UN system through an agreement with the UN under UN Charter article 57. There are fifteen specialized agencies, which perform functions as diverse as facilitating international travel, preventing and addressing pandemics, and promoting economic development. Funds, programmes, and other bodies The United Nations system includes a myriad of autonomous, separately-administered funds, programmes, research and training institutes, and other subsidiary bodies. Each of these entities have their own area of work, governance structure, and budget; several, such as the World Trade Organization (WTO) and the International Atomic Energy Agency (IAEA), operate independently of the UN but maintain formal partnership agreements. The UN performs much of its humanitarian work through these institutions, such as preventing famine and malnutrition (World Food Programme), protecting vulnerable and displaced people (UNHCR), and combating the HIV/AIDS pandemic (UNAIDS). Membership All the world's undisputed independent states, apart from Vatican City, are members of the United Nations. South Sudan, which joined 14 July 2011, is the most recent addition, bringing a total of UN member states. The UN Charter outlines the rules for membership: In addition, there are two non-member observer states of the United Nations General Assembly: the Holy See (which holds sovereignty over Vatican City) and the State of Palestine. The Cook Islands and Niue, both states in free association with New Zealand, are full members of several UN specialized agencies and have had their "full treaty-making capacity" recognized by the Secretariat. Indonesia was the first and the only nation to withdraw its membership from the United Nations, in protest to the election of Malaysia as a non-permanent member of the Security Council in 1965 during conflict between the two countries. After forming CONEFO as a short-lived rival to the UN, Indonesia resumed its full membership in 1966. Group of 77 The Group of 77 (G77) at the UN is a loose coalition of developing nations, designed to promote its members' collective economic interests and create an enhanced joint negotiating capacity in the UN. Seventy-seven nations founded the organization, but by November