A new achievement for Katy
@katyperry's Dark Horse tops the 5 million mark. It's her 6th song to sell 5 million -- more than any other artist.
US digital sales: Firework 6,622,000 | E.T. 5,736,000 | California Gurls 5,630,000 | Hot N Cold 5,511,000 | Roar 5,377,000 | Dark Horse 5,025,000.
source: https://twitter.com/chartnews