Indonesia is an independent republic consisting of more than 17,500 islands spread over 3,400 miles along the equator. The main islands are Java, Sumatra, Bali, Kalimantan (Borneo), Sulawesi (Celebes), Papua, Halmahera and Seram. The capital city of Jakarta lies in the lowlands of West Java, the most populated island. The country has approximately 251 million people, and more than 300 ethnic groups. It is the world's fourth-most populous country and boasts the largest economy in Southeast Asia with GDP growing at about 6 percent annually to about $895 billion in 2012. Indonesian is the country's official language. In tourist areas, English is commonly understood and spoken.