30103

medie2005 · 发表于 2008-12-21 14:08:35

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30103 is the only known multi-digit palindromic prime found by averaging the divisors of a composite number.
for example:
divisors of 149645: 1, 5, 173, 865, 29929, 149645
averaging the divisors of 149645 is :
(1+ 5+173+ 865+ 29929+149645)/6=30103.

divisors of 179574:
1, 2, 3, 6, 173, 346, 519, 1038, 29929,59858, 89787, 179574.
averaging the divisors of 149645 is :
(1+ 2+ 3+ 6+ 173+ 346+ 519+ 1038+ 29929+59858+ 89787+179574)/12=30103.

Question : Can the average of the divisors of other composite number to produce another pal-prime ?

无心人 · 发表于 2008-12-21 14:31:46

困难的很

northwolves · 发表于 2008-12-22 22:40:01

似乎除了穷举没有别的办法

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