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Please give me a detailed solution for the question

Let n > 18 be a positive integer such that n-1 and n+1 both are prime .

Prove that n has at least 8 different positive factors .

Darkside  Nov 9, 2018
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42 =2 x 3 x 7 =3 "Prime Factors"
Total divisors =The exponent of each "Prime Factor" + 1, all multiplied together: (1+1) x (1+1)x(1+1) =8 divisors:
1 | 2 | 3 | 6 | 7 | 14 | 21 | 42 (8 divisors), or factors.
42 - 1 =41 Prime number
42+1 =43 Prime number.

Guest Nov 9, 2018
edited by Guest  Nov 9, 2018

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