Demi Lovato is 21 - see 21 photos of birthday girl's cutest smiles

Slideshow posted in Photos | Tuesday, August 20, 2013

1 of 21: Demi Lovato poses with fellow 'X Factor' judge Simon Cowell at FOX's Upfront Presentation in New York on May 13, 2013. ( Photo / Kristina Bumphrey / Startraksphoto.com)