The mass of an electron in amu is :

Mass of electron in grams = 9.1×10^-28
1 amu = 1.67×10^-24 grams
Mass of electrons $=\frac{9.1\times {10}^{-28}}{1.67\times {10}^{-24}}=5.4\times {10}^{-4}\mathrm{amu}$