Exactly. This kata is too advanced for 6 kyu.

True.

DMorg, I didn't say that, at all. You said this wasn't a programming task and I disagreed.

much of a programmers work involves googling, there's no shame in that. but to answer your query:

choose a kata that you feel is worth your time. no one is compelling you to do number theory tasks

I disagree, you should use the right algorithm for the task at hand. And that's part of a programmer's work.