Prime numbers are numbers greater than one that is only equally divisible by the number itself or by one. One thing you should keep in mind is that 1 is not a prime number. One example of a prime number can be 17, which is considered a prime number because it is a number that can be divided by two numbers only which are 1 and 17. Have you wondered about what are rational numbers and how many rational numbers are there between 20 and 30? Keep reading to know them all, including the prime numbers between 20 and 30!

**1. How do you Find a Prime Number?**

The first method of finding a prime number involves **factorization** of the number and if there are more than 2 factors of a number then the number is not a prime number. The factors must be the number itself and 1. 2, 3, 5, 11, and 13 are some examples of prime numbers. The second method is used for larger numbers and involves various steps for identifying a prime number.

- Step 1 is checking if it is an even number as all even numbers except 2 are not a prime number as it is divisible by two.
- Step 2 involves adding the digits of the number and if the sum of digits of a number is a multiple of 3 then the number is not a prime number.
- Step 3 is identifying if the number is a multiple of 5, which can be done by checking the last digit of the number, if the number ends with a 0 or 5 then it is a multiple of 5.
- Step 4 requires you to find the square root of the number and if the square root of the number is divisible by any prime number smaller than the square root then it is also not a prime number.

If any specific number fulfills all the criteria mentioned in the steps then it can be termed a prime number.

**2. What are the Prime Numbers between 20 and 30?**

When a number can be divided by itself and 1 it is termed a prime number. So prime numbers between 20 and 30 can be found by eliminating all the even numbers as they are divisible by 2 therefore 22, 24, 26, and 28 are not prime numbers. Further numbers 21 and 27 are divisible by 3 so they cannot be prime numbers as well lastly, 25 is divisible by 5 so it is also not a prime number. This leaves us with the numbers **23, and 29** which are the 2 prime numbers between the two.

**3. What is the Sum of Prime Numbers between 20 and 30?**

After learning about the prime numbers between 20 and 30, let us now look at their sums. The numbers 23 and 29 are the only prime numbers falling between 20 and 30 which are divisible by 1 or themselves.

The sum of prime numbers 23 and 29 will be

23 + 29 = **52**.

This means that the sum of the prime numbers between 20 and 30 is 52. Must read How can You Find the Sum of the First 100 Natural Numbers?

**4. Which Number is exactly between 20 and 30?**

Numbers that come between 20 and 30 are as follows: 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, and 30.

To find an exact number between 20 and 30, add the first and the last numbers and divide the result by 2:

20 + 30 = 50,

50 ÷ 2 = 25

The exact number is **25**.

**5. What is the Difference between Two Prime Between 20 and 30?**

Now that you are aware of the sum of prime numbers between 20 and 30, let us now understand their difference. 23 and 29 are the two prime numbers that fall between 20 and 30:

29 – 23 = 6

23 – 29 = -6

This brings us to the conclusion that the difference between two prime numbers ranging from 20 to 30 can be either **+6 or -6**. (See How to do Addition using Standard Algorithm?)

**6. How many Rational Numbers are there between 20 and 30?**

A rational number refers to any number that can be written in a fraction form, i.e. in the form of p/q where q≠0 can be referred to as a rational number. Since any rational number can be divided into infinite parts of a fraction there exists an **infinite** amount of rational numbers between any two given rational numbers. Therefore between two integers such as 20 and 30, there exist an infinite amount of rational numbers.

**7. What are the Prime Numbers Between 20 and 35?**

Any number that can only be exactly divided by two natural numbers 1 and itself often known as the prime number. So prime numbers between 20 and 35 can be found by eliminating all the even numbers as they are divisible by 2, so 22, 24, 26, 28, 30, 32, and 34 are not prime numbers. Further numbers 21, 27, and 33 are divisible by 3 which means they won’t fall under prime numbers, lastly, 25 and 30 are divisible by 5 so it is also not prime numbers.

The remaining ones are **23, 29, and 31** which are the 3 prime numbers since they can only be divided by themselves and 1. Therefore, the prime numbers between 20 and 35 are 23, 29, and 31. Check out Which Correlation is the Strongest?

**8. What is the Prime Number Between 20 and 25?**

Now that you are aware of the prime numbers between 20 and 35, let us now focus on those that are between 20 and 25. To find what is the prime number between 20 and 25, you must know that there exists only one prime number because 20, 21, 22, 24, and 25 are somehow divisible by any other number apart from the actual number and one. This leaves us with the number **23** which is the only factor or prime number that cannot be divided by any other number apart from 1 and 23.

**9. What are the Prime Numbers Between 20 and 50?**

A prime number can only be divided by the number 1 and the actual number because it only has two factors. The prime numbers between 20 and 50 are **23, 29, 31, 37, 41, 43, and 47** since the others are divisible by numbers beyond 1 and themselves. Additionally, 251 is the total of all prime numbers between 20 and 50. Must learn What are the Factors of 80?

**10. What are the Prime Numbers Between 20 and 40?**

The four prime numbers that fall between 20 and 40 are **23, 29, 31, and 37**, which set them apart from all other numbers. All prime numbers between 20 and 40 add up to 120.

**11. What are the Prime Numbers Between 20 and 45?**

Six prime numbers reside between 20 and 45 which are as follows: **23, 29, 31, 37, 41, and 43** setting them up apart from the others. Furthermore, the total of all prime numbers between 20 and 45 is 204 and the average between them is 34.

A prime number can only be divided by one and the actual number. 1 is widely recognized as being non-prime among mathematicians. Zero is neither prime nor composite because it has an unlimited number of factors. You should be aware that the smallest prime number is 2 and the smallest composite number is 4 whereas, neither 0 nor 1 is a prime number or composite number. The next crucial point to remember is that all even numbers could be divided by two; thereby, all even numbers which are greater than two are composite numbers. (Also read What does How Many More mean in Math?)