Please answer a question about the following article about Tennessee:

According to the U.S. Census Bureau, as of 2015, Tennessee had an estimated population of 6,600,299, which is an increase of 50,947, from the prior year and an increase of 254,194, or 4.01%, since the year 2010. This includes a natural increase since the last census of 142,266 people (that is 493,881 births minus 351,615 deaths), and an increase from net migration of 219,551 people into the state. Immigration from outside the United States resulted in a net increase of 59,385 people, and migration within the country produced a net increase of 160,166 people. Twenty percent of Tennesseans were born outside the South in 2008, compared to a figure of 13.5% in 1990.

What was Tennessee's estimated population in 2015?
6,600,299