Python Program to Check Prime Number

We will write a program here in which we will check that a given number is a prime number or not.

Prime numbers:

If the natural number is greater than 1 and having no positive divisors other than 1 and the number itself etc.

For example: 3, 7, 11 etc are prime numbers.

Composite number:

Other natural numbers that are not prime numbers are called composite numbers.

For example: 4, 6, 9 etc. are composite numbers.

Let us look at the following example to understand the implementation.

Example:

# A default function for Prime checking conditions
def PrimeChecker(a):
    # Checking that given number is more than 1
    if a > 1:
        # Iterating over the given number with for loop
        for j in range(2, int(a/2) + 1):
            # If the given number is divisible or not
            if (a % j) == 0:
                print(a, "is not a prime number")
                break
        # Else it is a prime number
        else:
            print(a, "is a prime number")
    # If the given number is 1
    else:
        print(a, "is not a prime number")
# Taking an input number from the user
a = int(input("Enter an input number:"))
# Printing result
PrimeChecker(a)

Output:

Enter an input number:17
17 is a prime number

Explanation:

We have used nested if else condition to check if the number is a prime number or not.

First, we have checked if the given number is greater than 1 or not. If it is not greater than 1, then the number will directly come to the else part and print 'not a prime number.'

Now, the number will enter into for loop where we perform Iteration from 2 to number/2. Then, we used nested if else condition inside the for loop. If the number is completely divisible by 'i' then, it is not a prime number; else, the number is a prime number.

Next TopicPython all Prime Numbers between an Interval

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