Before the start of the season, Hamilton announced he would not be exercising his option of switching his car number to 1, as was his prerogative as reigning World Champion, and would instead continue to race with his career No. 44. It was the first season since , when Alain Prost retired from the sport following his fourth and final World Drivers' Championship title in , that the field did not contain a car bearing the No. 1. Hamilton dominated the season, winning ten races finishing on the podium a record seventeen times as he matched his hero Ayrton Senna's three World Championships titles. The rivalry between him and Rosberg intensified, climaxing in a heated battle at the US Grand Prix where Hamilton won in an action-packed, wheel-to-wheel battle with his teammate to clinch the title with three races to spare. That year, Hamilton extended his contract with Mercedes for three additional years in a deal reportedly worth more than £100 million, making him one of the best-paid drivers in Formula One, as well as allowing Hamilton to retain his own image rights, which is considered unusual in the sport, and keep his championship-winning cars and trophies.