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(another Prime Pages' Curiosity)
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340561 = 13 x 17 x 23 x 67 is the 2nd 4-Brilliant Carmichael Number (the first being 75361), and the first Carmichael Number that truncates to another Carmichael Number (to the first, 561). Its reversal is semiprime. Its digital sum (19) is prime. The sum of prime factors is 120 = 5! = 2^3 x 3 x 5, hence the mean of the prime factors is the primorial 30 = 2 x 3 x 5. [Carmichael]

 

  Submitted: 2004-11-05 10:31:29;   Last Modified: 2008-01-30 11:28:00.



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