The only perfect number between 20 and 50 is 28.
There are 4 numbers that are prime between the number 10 and 20. They are 11, 13, 17, and 19.
There are (not counting 1) three square numbers between 1 and 20.
20
There are 20.
There is an infinite number of numbers between 0 and 20.
20
20
20
20 number
There are 40 odd numbers between 20 and 100. Remember that an odd number is every second number. There are 80 numbers between 20 and 100, so there are 40 odd numbers and 40 even numbers.
8: 1,2,3,5,7,13,17,19