The singer, who celebrated her birthday on December 2, kicked off her big day by thanking fans for their well wishes and urged them to buy her new album, Britney Jean, which is releasing today, reported OK! magazine.
She took to Twitter and posted a photo of herself getting ready to cut her birthday cake with her band and dancers at the rehearsal space where she is preparing her Sin City show, which begins later this month.
"Amazing birthday surprise from my extended family," she posted.