23 is indeed prime, and 36 is indeed composite.
33 is composite, and 42 is indeed composite.
21 is composite, and 25 is composite as well
27 is not prime, and 39 is composite.
Primes have only 2 factors: 1 and themselves.
And 33, 21 and 27 definitely have more than 2 factors. Hope this helps!
~Just a joyful teen