‘21’ articulates Samia’s fear of turning 21, the age in America where you are considered a fully legal adult. She expressed to Fool’s Mag:

I felt I hadn’t quite caught up with the person that I imagined myself to be at 21… my barometer of success is a little bit fucked up in that kind of way. I saw a lot of 16-year-olds who had a lot of money and very fulfilling careers. I think I was just getting down on myself. In writing that song, I was giving myself a pep-talk about all of the great things I have been able to do up to this point.