"Stitches," however, wasn't one of those songs: that song was written without his help. Mendes takes pride in his songwriting abilities, though, and wasn't sure he wanted to record the song at first. Mendes told Radio.com, "I was thinking, I don't want to sing [it] because I only want to sing songs that I write."

Happily for him, he decided to keep an open mind. "I was like, 'Well, let me just listen to this,' and I fell in love. And man, it was just so cool to hear that. I remember before I heard it, I was like 'I really want to write a song where the bridge is a repetitive something, that just drills itself into your head.'"

And he found that bridge in "Stitches": "'Needle in a thread gotta get you outta my head.' When that bridge hit I was like, 'This is the song.' I had to have it."

Good call: the video has passed 27 million views. He's since released a video for a stripped down acoustic version of the song; that video has passed 5 million views. Mendes says its important to him that, no matter how much production is on any of his songs, he always wants them to hold up if he plays them acoustically. "Totally, absolutely 100%. Because that's what I do live, I bring my acoustic guitar on stage. If I can't bring it into that realm, then it's not going to be my song."