IT and the number 27
Pennywise resurfaces every 27 years.
The 2017 movie was released 27 years after the 1990 mini-series.
Bill Skarsgård is 27 years old.
Jonathan Brandis, who played the original Bill Denbrough, died at 27 years old.
The film was released this year on September 8th, or 08/09/2017, and add those numbers together and it makes 27.
Chapter 2 will be released on 06/09/2019 and those numbers also add up to 27.