• Why is primality test "dumb" ?

Question related to mission Prime Palindrome Golf

 

To check if it's prime is also very simple, but kinda dumb and slow.

This is a quote from hints. I understand slow, but why checking primality would be dumb ?

My best solution for primality is

all(n%x for x in range(2,n))

Is there another way to solve it ? If there is, I think I miss mathematical skills here...