10613583595427 is also a factor of 2^1968721+1
 

[QUOTE=storflyt32;359827]2^1968721+1 has a factor 3 ...[/QUOTE]

Correct! It has a factor of 10613583595427 as well. What is so interesting in this number?

2[SUP]2k+1[/SUP]=2 (mod 3), so 2[SUP]2k+1[/SUP]+1 will always be divisible by 3. Same as 2[SUP]2k[/SUP]-1, the last one is (2[SUP]k[/SUP]-1)(2[SUP]k[/SUP]+1), i.e. a product of two consecutive odd numbers, so one of them is divisible by 3.

So what? :razz:

I have discovered a fantastic new way to factorise numbers using absolutely no compute power whatsoever. Just post is here and give it some name like "Unwilling Number" and within a few hours it will magically be factorised for you. I hope no one has patented this new method yet.