I suggest you to check the next web site, where you can get more information related to your question:
Anyway, the answer to your question is:
Mass of proton : 1,6726 x 10^(-27) kg
Mass of neutron: 1,6749 x 10^(-27) kg
Mass of electron: 0,00091x10^(-27) kg
The mass of each particle is very small, so the number -27 means the power of 10 in every case.
As you see from this information, the mass of a neutron is greater than the mass of a proton because the neutron contains a proton, an electron, and some subatomic particles.
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