(CNN)Age ain't nothing but a number. In Billie Eilish's case though, it's a big deal.
The pop singer-songwriter is 17 years old and the first artist born in the 2000s to hit No. 1, thanks to her debut album "When We All Fall Asleep, Where Do We Go?"
She's also the youngest woman to hit No. 1 since 2009 when Demi Lovato debuted with "Here We Go Again" at 16.
Here's four other things you should know about Billie Eilish.