Write down separately the prime and composite numbers less than $20$.

Express the following as the sum of two odd primes.

$44$

Express the following as the sum of two odd primes.

$36$

Express the following as the sum of two odd primes.

$24$

Express the following as the sum of two odd primes.

$18$

Check whether the following number is a prime number or not.

$23$

Check whether the following number is a prime number or not.

$51$