This number is a prime.

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Let the cs(p) be the cumulative digit sum of all the primes 2 to p (e.g., cs(11)=2+3+5+7+1+1=19). There are the only four known primes such that cs(p)=2p; they are 5, 23, 47 and 163. [Vrba]

Submitted: 2006-12-26 08:09:36;   Last Modified: 2008-01-30 17:28:00.
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