What are the prime numbers between 20-30?

The numbers between 20 and 30 are:
${\displaystyle 21,22,23,24,25,26,27,28,29}$
Since even numbers are by definition divisible by 2, all even numbers other than 2 are not prime. This leaves us with:
${\displaystyle 21,23,25,27,29}$
${\displaystyle 21=3\times 7}$ - not prime
${\displaystyle 25=5\times 5}$ - not prime
${\displaystyle 27=3\times 9}$ - not prime
This leaves:
${\displaystyle 23,29}$
For both of these numbers the only numbers they are evenly divisible by is 1 and themselves.
Therefore, ${\displaystyle 23}$ and ${\displaystyle 29}$ are the prime numbers between 20 and 30.