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Prime-go-round (Posted on 2012-02-06) Difficulty: 3 of 5
For k=2,3,4,5,6 find an example (or prove absence) of a circular prime of k digits (i.e. a prime number that remains prime as its leftmost digit (Most Significant Digit) is moved in turn to the right hand side).

See The Solution Submitted by Ady TZIDON    
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Near misses -- Nihil ! Comment 2 of 2 |

This link provided some interesting information, including the tries below:  http://www.worldofnumbers.com/circular.htm

For k=8

     71777393 prime
     17773937 prime
     77739371 prime
     77393717 prime
     73937177 prime
     39371777 prime
     93717773 prime
but 37177739 = 29 * 683 * 1877

For k=7

a)   9197777 prime
     1977779 prime
     9777791 prime
     7777919 prime
     7779197 prime
     7791977 prime
but 7919777 = 83 * 95419

b)   9991313 prime
     9913139 prime
     9131399 prime
     1313999 prime
     3139991 prime
     1399913 prime
but 39991313= 17 * 235243

 


  Posted by xdog on 2012-02-07 20:02:26
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