AT&T Inc. is an American multinational telecommunications conglomerate, headquartered at Whitacre Tower in downtown Dallas, Texas. AT&T is the second largest provider of mobile telephone services and the largest provider of fixed telephone services in the United States, and also provides broadband subscription television services through DirecTV. AT&T is the third-largest company in Texas (the largest non-oil company, behind only ExxonMobil and ConocoPhillips, and also the largest Dallas company). As of May 2014, AT&T is the 23rd-largest company in the world as measured by a composite of revenues, profits, assets and market value, and the 16th-largest non-oil company. AT&T is the largest telecommunications company in the world by revenue. As of 2017, it is also the 18th-largest mobile telecom operator in the world, with 135 million mobile customers. AT&T was ranked at #4 on the 2017 rankings of the world's most valuable brands published by Brand Finance.