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.