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[ August 12, 1999 ] Palindrome  21312  is another unique one
when taken into consideration the following two rules :
First, the digit zero may not appear in the palindrome
Secondly, the sum of its digits equals the number of its prime factors
21312 = 2 + 1 + 3 + 1 + 2 = 9 so there should exist nine prime factors !
Indeed as 21312 = 2 x 2 x 2 x 2 x 2 x 2 x 3 x 3 x 37.
Dear puzzlers, proof me wrong by finding a second solution...

P.S. 21312 is also the largest substring in 249 or 562949953421312 ( A046260 )
(Note for the insiders : 21312 equals 32 times the number of the beast 666!)

A000059 Prime Curios! Prime Puzzle
Wikipedia 59 Le Nombre 59 Numberland 59














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