There is a website all YouTube Partners gain access to (I can't even remember the name of it and I am a partner) and they have 50,000 + songs for YouTubers to use with no copyright. I'm going to assume it is from there, so in theory the song has no name. The only way you'd be able to get it so to either ask PewDiePie himself, or gain access to the Partner Music Library.

To live is to die and to die is to live. Emotionless Love is not Love at all.