The Antikythera Mechanism, as we know it today, consists of approximately 40 cooperating gears. Each pair of gears makes a division according to the number of teeth of the meshing gears. This calculation is then fed to the next set until it reaches the final axis, and hence pointer, indicating an event which is read off a dial. Hence, it is a modular calculator with its complexity increasing with the number of gears.
As an example, a simple division of 40/60 can be done with a pair of gears with 40 and 60 teeth, or simply with 20 and 30 teeth. For calculations involving prime numbers, however, one cannot simplify further. This is the reason why one finds gears with 53 or 223 teeth etc. on the original mechanism.