This weekend on The iHeartRadio Countdown with Mario Lopez Niall Horan will be checking in! He just dropped his new song 'Slow Hands' on Thursday and he's currently working on his debut album as well. So we'll catch up with him and find out if Ed Sheeran can somehow remain at the #1 spot for a 13TH STRAIGHT WEEK! Unbelievable really. Plus we countdown the rest of the top 20 and play some of your favorite throwback tracks! Tune in!