Answer:
We know that the electronic charge is 1.6 E-19 coulombs
Therefore 1 coulomb of charge contains 1.6 E19 electrons
A charge of 16.7 E6 coulombs therefore contains
N = 16.7 E6 * 1.6 * E-19 = 2.67 E-12 electrons
Also, the charge on the proton equals that on the electron