Program to check if the given number is Prime or not in Python

November 12, 2021

Prime or not in Python

In this article we will see a program to find whether a number is Prime or not in Python. A number is said to be a prime number if and only if it is only divisible by 1 or itself (factors==>1,number itself) . If a number has more than two factors than the number is said to be not a prime number.

Sample input: 17
Sample output: The given number is prime

See the two different approaches below , solution 1 is more efficient than solution 2

Method 1

Algorithm:

Step 1: Initialize the variable a and count to zero
Step 2: Read the input
Step 3: Set a to n//2 (// in python implies integer division) , we can make a to square root of number to make it more efficient
Step 4: iterate through 2 to a+1 and check whether it is divisible by i or not
Step 5 : if divisible , then print “not a prime number” and set count to 1 and break from the loop
else continue iteration
Step 6 : if count is still zero then the given number is prime number

Python code:

a = 0
count = 0
n=int(input("Enter the number to check if it is prime or not: "))
a = n // 2;

for i in range(2,a+1):
    if (n % i == 0):
        print("The given number is not prime")
        count = 1
        break
if (count == 0):
    print("The given number is prime")

Enter the number to check if it is prime or not: 17
The given number is prime

Method 2

Algorithm

Step 1: Take an empty array
Step 2: Read the number
Step 3: Iterate a from 1 to the number
Step 4: If number is divisible by iterator i then append the number to factors array
Step 5: if length of factors array is 2 then given number is prime
else the given number is not prime number
(for more clarity factors of numbers also printed)

Python Code:

factors=[ ]
n=int(input(“Enter the number to check if it is prime or not: “))
for i in range(1,n+1):
    if (n % i == 0):
        factors.append(i)
if (len(factors)==2):
    print(“The given number is prime”)
else:
    print(“The given number is not prime number”)
print(“Factors of given number is”,factors)

Enter the number to check if it is prime or not: 16
The given number is not prime number
[1, 2, 4, 8, 16]

Positive or Negative number: C | C++ | Java
Even or Odd number: C | C++ | Java
Sum of First N Natural numbers: C | C++ | Java
Sum of N natural numbers: C | C++ | Java
Sum of numbers in a given range: C | C++ | Java
Greatest of two numbers: C | C++ | Java
Greatest of the Three numbers: C | C++ | Java
Leap year or not: C | C++ | Java
Prime number: C | C++ | Java
Prime number within a given range: C | C++ | Java
Factorial of a number: C | C++ | Java
Sum of digits of a number: C | C++ | Java
Reverse of a number : C | C++ | Java
Palindrome number: C | C++ | Java
Armstrong number : C | C++ | Java
Armstrong number in a given range : C | C++ | Java
Fibonacci Series upto nth term : C | C++ | Java
Factorial of a number : C | C++ | Java
Power of a number : C | C++ | Java
Factor of a number : C | C++ | Java
Strong number : C | C++ | Java
Perfect number : C | C++ | Java
Automorphic number : C | C++ | Java
Harshad number : C | C++ | Java
Abundant number : C| C++ | Java
Friendly pair : C | C++ | Java

21 comments on “Program to check if the given number is Prime or not in Python”

Mahima
def prime(n):
if n==1:
return False

else:

for i in range(2,int(n**(1/2)+1)):
if(n%i==0):
return False

return True

n = int(input(“Enter the integer number:”))
if(prime(n)):
print(“The number is a Prime”)
else:
print(“The number is not a prime”)

0

Log in to Reply
Iqra
Let’s Try it!
n=int(input(“ENTER the number for check prime or not:”))
for i in range(2,n):
if(n % i ==0):
print (“Given number is not prime”,end=” “)
break
else:
print(“Given number is PRIME”)

1

Log in to Reply
rajat
More easy solution for the Solution 1:
x = int(input(“Enter the number:”))
for i in range(2, x):
if x % i == 0:
print(“Not Prime”)
break
else:
print(“Prime”)

0

Log in to Reply
VIKRANT
a=int(input())
b=2
c=3
d=5
e=7
if ((a==b)or(a==c)or(a==d)or(a==e)):
print(“the number is a prime number”)
elif ((a%b==0)or(a%c==0)or(a%d==0)or(a%e==0)):
print(“number is not a prime number”)
else:
print(“the number is a prime number”)

0

Log in to Reply
RishiRanjan
n=int(input(“Enter a Number for finding PrimeNumber:-“))
if n<2:
print(n, "is not a prime number")
else:
for i in range(2,n):
if(n%i==0):
print(n, " is not a prime number")
break

else:# this for part else not of if part because if part break

print(n, " is prime number")

0

Log in to Reply
Shubham
num=int(input())
if num%2==0 and num!=2:
print(“not prime”)
else:
print(“prime”)

0

Log in to Reply

Shubham
num=int(input(“Enter the value:”))
prime=True
for i in range(2,num):
if num%i==0 and num!=2:
prime=False
break
if prime:
print(“This no. is prime”)
else:
print(“This no. is not prime”)

0

Log in to Reply

gaurav
n = int(input(“Enter num: “))

i = 2
while i < n:
if (n%i) == 0:
print("not a prime number")
exit()
i+= 1
print("prime number")

1

Log in to Reply
pavan
easy one
x=int(input(“Enter the number:”))
for i in range(2,x):
if(x%2==0):
print(” not a prime”)
break
else:
print(“prime”)

0

Log in to Reply
Aruna
num = int(input( “Enter a number”))
if num >1:

for i in range (2, num):
if (num % i) == 0:
print (” its not a prime number”)
break
else:
print (“its a prime number”)

else:
print(“its not a prime nor composite number”)

0

Log in to Reply
Sourabh
another approach:
n = int(input(‘enter the num’))
for i in range(2, n+1):
if n % i == 0:
break
if n == i:
print(n, ‘is prime’)
else:
print(n,’is not prime’)

0

Log in to Reply
Rohit
n=5
c=0
for i in range (1,n+1):
if (n%i==0):
c=c+1
if c==2:
Print (n,” is leap year”)
Else :
Print (n,” is not a prim”)

0

Log in to Reply
Rohit
n= int(input(“enter a no.”))
i=1
c=0
while i<=n:
if n%i==0:
c=c+1
i=i+1
if c==2:
Print(n,"is prime no.")
else:
Print(n," is not a prime")

0

Log in to Reply