>>13330293In your case, 19(base 10) =/= 19(base 16). So you are not even comparing the same number, so it makes no sense. Now, 19(base 10) = 13(base 16) and 13(base 16) is still a prime number.
Now, 23(base 16) looks like a prime number, but only if you assume that the base is 10(which is not). So it is just easy to identify small primes in base 10 because we are used to them, but if you convert exactly(and not just changing the base but keeping the number) primes numbers keep being primers no matter the base.
