Ain't Giving Up Craig David & Sigala
Kesha's debut track Tik Tok was the biggest-selling digital single in the world last year.
It sold 12-point-8 million copies - three million more than Lady Gaga's Poker Face, which topped the chart in 2009.
Lady Gaga's at number two this time - with Bad Romance, and number four with Telephone.
The sales figures have been released in the annual digital musical report published by the International Federation of the Phonographic Industry (IFPI).
The top-10 digital single worldwide in 2010 were: