Djokovic takes Federer's world number one record, eyes Grand Slam history
He is also a year younger than Rafael Nadal who also has 20 majors.
"Now that I've become the historic No.1, I'm relieved," said Djokovic after sweeping to a ninth Australian Open last month which guaranteed his extended stay at the top.
"Now, I'm going to be able to focus mainly on the Grand Slams."
Djokovic reclaimed the top ranking from Nadal in February 2020 and finished as year-end number one for the sixth time, tying the mark set by Pete Sampras.
He is currently in his fifth different spell atop the rankings.
Nadal, currently at number two, has been at the top for 'only' 209 weeks in total although the 13-time Roland Garros champion can boast being a top 10 ever-present since April 2005.
He will, however, lose his world number two spot to Daniil Medvedev a week on Monday.
Federer, who returns to action in Doha next week after more than a year out of action to recover from two knee surgeries, will slip out of the top five on Monday.
Djokovic made his top 100 debut in July 2005, just weeks after Nadal had won his first Roland Garros.
He was top 50 in June 2006, top 20 for the first time in October 2006 and top 10 by March 2007.
He first became world number one at the age of 24 on July 4, 2011, the day after winning Wimbledon for the first time, beating Nadal in the final.
- Brief dip and swift return -
Only a six-month injury absence in 2017 saw his ranking plunge, all the way to 22 the following summer.
It was just a blip -- Djokovic was back at number one again by November and with the exception of November 2019 until January last year, when Nadal reclaimed pole position, he has been rock solid.
In head-to-heads, he leads Federer 27-23 and has won all six of their last meetings at the majors, including 2019's epic Wimbledon final where he saved two match points.
Against Nadal, he has a 29-27 lead and is still one of only two men to have beaten the Spaniard at Roland Garros since 2005.
At least Nadal, however, can boast comfortably seeing off Djokovic in the 2020 Roland Garros final, denying the Serb the opportunity to become the first man in half a century to win all four Slams more than once.
His Wimbledon total stands at five to Federer's eight and Nadal's two.
At the US Open, he has three to Federer's five and Nadal's four.
"Obviously I have in my mind to win more Grand Slam titles and to break records.
"Until I retire from the tour, I will be devoting most of my attention and energy to winning the other major titles," Djokovic said.