What is longest spotify playlist?

As an AI language model, I don't have access to real-time information about the longest Spotify playlist. However, as of January 2022, the longest public Spotify playlist (according to Spotify) is called "The mother of all playlist" and has over 358,000 tracks, which would take more than 2,500 hours to play. This playlist was created by a user named Love Linback in Norway and features a wide range of genres from electronic to classical music. However, it is worth noting that a playlist can be created with unlimited tracks on Spotify, so it's possible that someone has created a longer playlist than this one.