It should be enough. Either it's not as optimized as you think, or you have some bug.

BTW this kata does not need a direct primality check, maybe your approach is not the best one?

You're welcome. I've also edited my posts accordingly.

Yes, you are correct, I had misinterpreted the test results and misread that aspect of the instructions. Apologies if I waylaid anyone and thanks for catching it.

In case 109 is the test which his code is failing:

For incrementing sequences, 0 should come after 9, and not before 1, as in 7890.

See this note, 67890 is incrementing, 67888 is upcoming incrementing, both tests are ok.

109 isn't decrementing, because of the other note:

For decrementing sequences, 0 should come after 1, and not before 9, as in 3210.

it can't be decrementing by definition.

Edit - ok, i'm seeing it more clearly... it doesn't wrap around but it can end it zero .I'll edit my response

Edit - Without more information from OliverS-K we can't conclude 109 is the case his code is failing, but that's a possibility.

Edit -

My response here was incorrect as per the instructions. 109 should not be considered interesting because decrementing sequences shouldn't wrap around.

Print the input, check why your code is failing: https://github.com/codewars/codewars.com/wiki/Troubleshooting-your-solution#print-input

If it says upcoming, 2 is not the right answer.