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Never prime! (Posted on 2004-04-29) Difficulty: 3 of 5
12 can be made into a prime by changing the 2 to 3; likewise, 63 can be changed into a prime by changing the 6 to 7.

What is the smallest number that cannot changed into a prime by changing a single digit?

Are there infinitely many such numbers?

See The Solution Submitted by Federico Kereki    
Rating: 3.8333 (6 votes)

Comments: ( You must be logged in to post comments.)
  Subject Author Date
answerK Sengupta2007-11-23 04:29:11
Extremely Simple part 2Geoff2004-05-06 06:14:29
Some Thoughtsre(2): Another thought - A simple solution for the 2nd partFederico Kereki2004-04-30 18:25:55
re: Another thought - A simple solution for the 2nd partRyan2004-04-30 16:40:21
re: A simple solution for the 2nd partRyan2004-04-30 14:52:29
Some ThoughtsA simple solution for the 2nd parte.g.2004-04-29 14:58:54
re: 2nd partRyan2004-04-29 11:33:12
Solution2nd partCharlie2004-04-29 11:25:55
Hints/Tips1st partSaka Devi2004-04-29 08:37:18
Some ThoughtsFirst approache.g.2004-04-29 08:25:59
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