Miley Cyrus turns 21/Reuters
Miley Cyrus turns 21 (Reuters)

Pop star Miley Cyrus will ring in her 21st birthday with an eight-hour party at the MTV studios.

"The TV party will begin with 21 Candles: Miley's MTV Moments, an hour-long special highlighting the 21 reasons why fans love the megastar, including Miley's best MTV moments of all time," MTV said.

Also featured will be clips from her music videos and performances as well as comments from celebrities. Cyrus will also re-air MTV's documentary Miley: The Movement Deluxe Edition, with new commentary and will also roll out episodes of her favourite MTV shows, Snooki & JWoww and Awkward.

Her celebration comes towards the end of an eventful year that saw her split with fiancé Liam Hemsworth and provoke a media storm with a highly sexualised video with Robin Thicke.

Cyrus, who broke down on stage at the iHeartRadio Music Festival in Las Vegas recently, maintained that she was happy. "I'm exhausted from being so f******g happy," she tweeted. "In bed at 9:45 & it feels so good. #booksinbed.''

Cyrus and Hemsworth met on the sets of the 2010 romantic drama The Last Song and began dating soon after.

The former Disney star was once the face of family TV series Hannah Montana but her more recent public appearances, film and television roles and concert performances have been criticised as setting bad examples for young girl fans. Her sexually provocative photoshoot with Terry Richardson also drew criticism as did her performance at the MTV VMAs with Thicke which led to some viewers demanding police action over her raunchy dance routine.