Photo: Capital Records/Universal Music

By Sierra Marquina

Katy Perry phoned in to On Air with Ryan Seacrest to celebrate her 11th hit on American Top 40 and her upcoming Prismatic World Tour.

The singer’s latest hit, “Dark Horse,” has catapulted to the top of the charts … and it actually came as a surprise to Katy.

“It’s so crazy because we never planned for this to be a single and we never knew it would have this kind of attention on it,” she says of the collaboration with Juicy J. “I was all up in the ‘Unconditionally‘ world and excited to be doing a ballad and then all of a sudden the demand for this song started rising and it was literally a dark horse … I’m such a control freak and I like to plan out everything. I was like, ‘Wait, what’s happening?’”

“Dark Horse” is just one of the hit songs Katy will be performing when she hits the road in May for her Prismatic World Tour.

“I’m actually building stamina right now [for the tour.] It kicks off in May … it goes from May 2014 until probably summer 2015 … we are kicking it off in the UK and then we come to the U.S. all summer long.”

Katy’s already revealed a prism-looking set design and now tells us she’s gearing up for all the details, especially the costumes.

“I’m in the middle of all the different plans and costumes and there are so many fun parts of the show. There’s about five or six sections and one of my favorite sections is the … ’Cat-ture‘ section [like couture] … you know me, queen of cats … it’s so fun, visual, and vibrant.”

Aside from securing her 11th hit, Katy also is the first person to reach over 50 million Twitter followers … yes, that is 5-0 million.

“It’s really terrifying sometimes,” she laughs. “Can you imagine if my butt tweets itself? Or honestly to tell you the truth, I’m double checking, like don’t tweet that picture.”

For tickets to Katy’s tour, click here!