Problems & Puzzles: Puzzles

Puzzle 1101 Primes p that divide the concatenation of sigma(p-1) and sigma(p+1) Giorgos Kalogeropoulos sent the following nice puzzle Primes p that divide the concatenation of sigma(p-1) and sigma(p+1)   Prime number 4793 divides the concatenation of sigma(4793-1) and sigma(4793+1)  where sigma(n) is the sum of the divisors of n.    sigma(4792) = 9000 sigma(4794) = 10368 900010368 = 2^7 * 3^2 * 163 * 4793   Q. Is this the only prime with this property?

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During the week from 3-9 Sept. 2022, contributions came from Michael Branicky

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Michael wrote:

2 is also a solution since sigma(1) = 1, sigma(3) = 4 and 2 divides 14.

No other prime terms found < 1.1 * 10^10.

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