General: "what you search for is the absolute maximum possible" sum. quoted from @Blind4Basics

Please add the above to original kata description, it would save people time :)

Not sure what do you mean by not working? it seems to be working

Definitely the description of this kata need more words! But it's surely a great one for mathematicians. A little more words here:
A sucessive power is an increment of the power provided as a parameter p, each time you iterate on "89" two iteration for this example, you will increment the power. Once out, k = sum of the new array(powered numbers) / the original number n, then if the multiplication of k*n == sum you are good, otherwise return -1