The country also has five populated and numerous unpopulated territories in the Pacific and the Caribbean. At 3.80 million square miles (9.85 million km2)[20] and with over 320 million people, the United States is the world's fourth-largest country by total area and third most populous. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many countries.[21] The geography and climate of the United States are also extremely diverse, and the country is home to a wide variety of wildlife.[22]