Starting with a prime digit add another digit, after or before the first, then another, adding it after, before or within the second number, and continue, keeping the resulting numbers prime, without repeating any of the digits you have used so far.

Example: 2, 23, 263, 2063, 29063....

Obviously you cannot reach a pandigital number (it will always be divisible by 9) .

What are the lowest and highest numbers in the set of eligible solutions with the maximum number of digits?

Please specify the interim stages leading to your results.

3, 31, 431, 4231, 40231, 402361, 4023671, 40236971

Posted by xdog on 2011-03-04 15:57:06