My bad, sorry. It seems like I didn't pay much attention to the description and the underlying theory. All good. Thanks for replying.

sorry - it's correct. n > 1

Which language? Which input? Which error?

Why? Which language?

Is it possible to correct the test? the '1' is not correct.

Yes problem with between/3...

Try it ;-) It was just the first dirty fix I thought of. But you'll need to add the compound test back in to see the effect.

OK. I looked at your solution; why have you thought to eval a compound? You could have directly begun with: prime_factors_(N, 2, "", R)..

Given a positive number n

17*17*93*677 is a positive number = 18195729:-)
I don't know how your function works but I don't see any problem with that... nevertheless I replaced it by its value: 18195729.

Given a positive number n

Because it doesn't make sense. A number != a compound, and some functions don't accept compounds. It would be similar if you passed in a string and didn't mention it could happen. IDK how valid it is to mix compounds and numbers in Prolog, but I would take a wild guess that it isn't. As you can see here(at the bottom), these are 2 different types.

It is a product... Why is it a problem for you? Others passed fine this part.

Thanks a lot

But you only see a few test cases. When you submit, there's probably hundreds of these tests run. So, is it really fast enough? :P

I have tried all the test cases in my python shell and it's working fast.I don't get it what is making my code slow here