Simply add a print statement at the beginning of your function, for example:

def increment_string(strng):
    print(strng)    # <---
    # your code...
    return strng

print(strng)

Not a kata suggestion.

It says in the description, that you should not iterate through all numbers from 1 to the input number.
You have to come up with a way to reduce the upper bound of your range of numbers to check.
Ask yourself the question :
What is the largest possible number that could be a divisor of x, that i NEED to check.