She is #1 now with her first solo album ''Stars Dance'' came out last week. She passed Jay-Z's album ''Magna Carta... Holy Grail''.
''Stars Dance''s 97.000 copy already sold out. This was the biggest birthday gift for her.
According to Billboard, she is ''The Youngest Female Singer'' since 2010. Her bff Taylor Swift had has the title in 2010.
Her new single ''Slow Down'' is a good song. Music video is cool and energetic. If you haven't listened yet, you should do. Here you are: