The normal number of exposures for a 35 mm film is up to 36. This is due to a variety of convenience and design constraints, you can only fit so many exposures in the cartridge, and 36 exposures make it suitable to take photographs and change film if you want to. For example, when you have 50 exposures and want to change film because you desire a faster emulsion, you will be wasting 20 exposure.
Yes, there are other types of cartridges with different no. of exposures to meet your requirements, so it’s better to look for the perfect one, before aiming your camera.