Just how big is Katy Perry? In an era when record sales are in unrecoverable free fall, her first album, One of the Boys(2008)—or her second, if you count the eponymous 2001 gospel record that she released under her birth name of Katy Hudson—sold more than five million copies. Her second (or third), Teenage Dream (2010), has sold almost as many, but even more significantly, digital sales of individual songs off the record have reached upwards of 28 million, buoyed by the near-ubiquity of five No. 1 singles (“California Gurls,” “Teenage Dream,” “Firework,” “E.T.,” and “Last Friday Night [T.G.I.F.]”), and placing it in a tie with Michael Jackson’s Bad(1987) for spawning the most No. 1 singles from the same album.