Python Program to Check Prime Number

What is Prime Number?

A positive integer greater than 1 which has no other factors except 1 and therefore 
the number itself is named a prime number. 2, 3, 5, 7 etc. are prime numbers as they 
are doing not have the other factors. But 6 isn't prime (it is composite) since, 2 x 3 = 6.

Source Code

# Python program to see if the input number is prime or not

num = 407

# take input from the user

# num = int(input(“Enter a number: “))

# prime numbers are greater than 1

if num > 1:

# check for factors

for i in range(2,num):

if (num % i) == 0:

print(num,”is not a prime number”)

print(i,”times”,num//i,”is”,num)

break

else:

print(num,”is a prime number”)

 

# if input number is less than

# or adequate to 1, it’s not prime

else:

print (num,”is not a prime number”)

Output

407 is not a prime number

11 times 37 is 407

In the above program, variable num is checked if it's prime or not. Numbers but or adequate 
to 1 aren't prime numbers. Hence, we only proceed if the num is bigger than 1.
We check if num is strictly divisible by any number from 2 to num - 1. If we 
discover an element therein range, the amount isn't prime. Else the number is prime.

We can decrease the range of numbers where we glance for factors.

In the above mentioned program, our search range is from 2 to num - 1.

We could use the range, [2, num / 2] or [2, num ** 0.5]. The later range is 
predicated on the very fact that a number must have an element but root of that number;
 otherwise the amount is prime.

You can change the worth of variable num within the above ASCII text file and test for 
other integers (if you want).