Sept 15 (Reuters) - Following is a selection of records held by world number one Novak Djokovic: * Most Grand Slam titles won (20 - tied with Roger Federer and Rafa Nadal) * Most number of weeks as the world number one (338) * Only player in the Open Era to win all four Grand Slam titles at least twice Sept 15 (Reuters) - Following is a selection of records held by world number one Novak Djokovic: * Most Grand Slam titles won (20 - tied with Roger Federer and Rafa Nadal) * Most number of weeks as the world number one (338) * Only player in the Open Era to win all four Grand Slam titles at least twice * Most Australian Open titles (nine) * Most Grand Slam finals reached (31 - tied with Federer) * Only player to reach at least nine semi-finals at all four Grand Slams * Only player to reach at least six finals at each Grand Slam * Most number of ATP Masters titles won (36 - tied with Nadal) * Only player to win all nine ATP Masters tournaments twice * Only player to win six ATP Masters titles in a single season (2015) * Won 31 consecutive matches at ATP Master tournaments* Only player to win the season-ending ATP Finals four years in a row (2012-2015) * Beat all top 10 players in a single season (2015) * Most ATP Player of the Year awards (six - tied with Pete Sampras)