The drop limit is 63 and the inversion limit is 31, even though you can build coasters that greatly exceed one hundred and possibly even one thousand of both. The track length has a limit as well, and although I don't know what the exact number is, if your track exceeds that length, it will actually display the track length as a negative number!
I built this little death machine in 2013. The ride is over 12 minutes long with an average speed of well over 100 MPH (160 km/h). The track length was claimed to be about -29,000 ft, indicating that it exceeded the limit by 29,000 feet.
More recently, I started a much larger project to create a coaster that takes up every square of a maximum-sized park, but that will take eons to complete. Eons of patience.