Justin Bieber and Selena Gomez celebrated her 21st birthday together, despite her claiming in interview after interview that she's single. You know what that means, right?

Ex boyfriend booty calls.

Radar Online reports that Bieber joined Gomez, who, like many young, entitled ladies celebrated her birthday (July 22) for an entire week, at Revolve Beach House on Saturday night (July 27).

Gomez's family attended the bash, and when her mom and stepdad left, that's when the party got really poppin', with Bieber roling up in his Godforsaken leopard print Audi R8.

Jaden Smith and Bieber's onetime "swagger coach" Ryan Good were also on hand to party.

And the party didn't stop, either. When the club closed down, E! Online reports that Gomez and Bieber left together -- and spent the night at his Calabasas, Calif. mansion.

But they're totally not together. Because, you know, her album dropped already.