perplexus.info :: Numbers : Never prime!

Home > Numbers

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: ( Back to comment list | You must be logged in to post comments.)

re: 2nd part

| Comment 4 of 12 |

(In reply to 2nd part by Charlie)

I'm glad I posted my answer first using 2310 instead of 23100. ;-)

Posted by Ryan on 2004-04-29 11:33:12

Please log in:

Forums (0)
Newest Problems
Random Problem
FAQ | About This Site
Site Statistics
New Comments (3)
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox:


perplexus dot info