Just an observation... I find long chapters tiring. I am the type of readers who like to read until a chapter ends before I put it down and go to sleep. I don't like to stop mid-chapter. If I see that the chapter is 40 pages long, I'll bulk.... unless it's REALLY well written, keeping me turning pages after pages, then I probably won't even notice the chapters, let alone their lengths.
Otherwise, I think a 100,000w book (about 400 printed pages) can use more than 20 chapters. Just my thought. My 75,000w novel has 38 chapters -- some are long (over 10 pages but less than 20), and some are short (less than 2 pages).
If you can put a hook in so they'll turn pages, good. But if you can give them a place to breathe and put down the book if they have to (and can't wait to get back to it), that's good, too.