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Never prime! (Posted on 2004-04-29)

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
solution for part (b)	K Sengupta	2022-09-11 01:05:33
Explanation to answer for part (a)	K Sengupta	2022-09-09 22:49:15
answer	K Sengupta	2007-11-23 04:29:11
Extremely Simple part 2	Geoff	2004-05-06 06:14:29
re(2): Another thought - A simple solution for the 2nd part	Federico Kereki	2004-04-30 18:25:55
re: Another thought - A simple solution for the 2nd part	Ryan	2004-04-30 16:40:21
re: A simple solution for the 2nd part	Ryan	2004-04-30 14:52:29
A simple solution for the 2nd part	e.g.	2004-04-29 14:58:54
re: 2nd part	Ryan	2004-04-29 11:33:12
2nd part	Charlie	2004-04-29 11:25:55
1st part	Saka Devi	2004-04-29 08:37:18
First approach	e.g.	2004-04-29 08:25:59

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