Please explain this :"

D e a r S t u d e n t, S o l u t i o n) a) x = 21600 x = 6^{3} \times 10^{2} x = 2^{5} \times 3^{3} \times 5^{2} N o . o f d i v i s o r s = (5 + 1) (3 + 1) (2 + 1) = 6 \times 4 \times 3 = 72 T h e r e f o r e, S u m o f d i v i s o r s = (2^{0} + 2^{1} + 2^{2} + 2^{3} + 2^{4} + 2^{5}) (3^{0} + 3^{1} + 3^{2} + 3^{3}) (5^{0} + 5^{1} + 5^{2}) = (\frac{2^{6} - 1}{2 - 1}) (\frac{3^{4} - 1}{3 - 1}) (\frac{5^{3} - 1}{5 - 1}) = 63 \times 40 \times 31 = 78120 R e g a r d s!

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