Prime Numbers

Those natural numbers which are greater than 1 and having only two factors are called prime numbers. One factor is '1', and the other is 'number itself'.

Those natural numbers which are greater than 1 and having more than two factors are called composite numbers.

For example:

The number 7 has only two factors 1 and 7, so it is a prime number.

The number 9 has more than two factors. It has three factors 1, 3, and 9. So 9 is not a prime number.

Note: 1 is neither the composite number nor a prime number.

Following are the first ten prime numbers:

2
3
5
7
11
13
17
19
23
29

List of Prime Numbers from 1 to 100

• There are 25 prime numbers between 1 and 100.
• Following table shows the prime numbers from 1 to 100:

List of Prime Numbers From 101 to 1000

How to Calculate the Prime number

If we want to check the given number is prime or not, then we have to follow the following steps:

1. Firstly, we have to write the factors of the given number.
2. Then, we have to count the found factors.
3. If there are exactly 2 factors of the number, then the number is prime. Otherwise, it is a composite number.

Solved Questions of Prime Numbers

Example 1: Is the number 8 prime or NOT?

Solution:

The given number is 8.

The factors of 8 are

1, 2, 4, and 8.

Thus the number 8 has 4 factors.

Since the number of factors of 8 is NOT exactly 2, so it is NOT a prime number (so

8 is a composite number).

Answer: 8 is not a prime number.

Example 2: Is the number 29 prime or NOT?

Solution:

The given number is 29.

The factors of 29 are

1 and 29.

Thus the number 29 has exactly 2 factors.

Since the number of factors of 29 is exactly 2, so it is a prime number.

Answer: 29 is a prime number.

Example 3: Which of the following given numbers are prime?

1, 7.3, 17, 18, 23, 25, 71, 4/5, 100, 123.

Solution:

17, 23, 71 are prime numbers.

The factors of these numbers are 1 and the number itself. So, these above numbers are prime.

And, the numbers which are left are not prime numbers.

1: It is not greater than 1

7.3: It is a decimal number

18: Factors of 18 are 1, 2, 3, 6, 9, and 18.

25: Factors of 25 are 1, 5, and 25.

4/5: It is not a whole number

100: Factors of 25 are 1, 2, 4, 5, 10, 25, 50 and 100.

123: Factors of 25 are 1, 3, 41, and 123.