By default, you cannot change the number of mappers, because it is equal to the number of input splits. However, there are different ways in which you can either set a property or customize the code to change the number of mappers.
For example, if you have a 1GB file that is split into eight blocks (of 128MB each), there will only be only eight mappers running on the cluster. However, there are different ways in which you can either set a property or customize the code to change the number of mappers.
