Miley Cyrus has been hard at work promoting her new single, "We Can't Stop," and, according to a source, she finally took the time to celebrate the song's success by partying with pal Justin Bieber at Beacher's Madhouse in Los Angeles Saturday night.

So does this mean that they're a couple?

"I'm engaged. I'm engaged!" she told D.C.'s Hot 99.5 radio station. "That's impossible."

Click here to listen to Cyrus' new hit single .

But that doesn't mean she can't have fun with a male friend, too. Cyrus, 20, was dancing to her track around 11:30 p.m. when Bieber, 19, arrived with rapper Lil Twist and a full security team, according to the source.

The singers, who are longtime friends, were "dancing and twerking along to the new single on repeat with Beacher's crew of Oompa Loompas," the insider added.

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