Related Tags

circular
prime
algorithm

# What is a circular prime? Educative Answers Team

A number is said to be a circular prime if all its possible rotations are also prime numbers. ## Algorithm

• First, divide the number into its digits.
• Then, make all possible rotations with those digits.
• Now, check whether or not each possible rotation is a prime number.

## Code

In the code below, we have used the is_prime() method to check whether or not a number is prime. In order to get our new rotation, we simply get the last digit of the number and place it at the start.

# Function to check a number is a circular
# prime or not
# number is passed as a string, so number of
# digits is evaluated easily.
def is_circular_prime(number):
i = remainder = value = total = 0
digits = len(number)
num = int(number)
# Here we will pick the last digit and
# place it at the start in order to form
# a new rotation.
# 199 -> 919 -> 991
while i < digits:
# Dividing the number in digits
# 199 % 10 = 9(last digit)
remainder = int(num % 10)
num = int(num / 10)
num = int((remainder * (10 ** (digits - 1)) + num))
print(num)
value = is_prime(num)
total += value
i += 1
if total is digits:
print("Circular Prime")
else:
print("Non-Circular Prime")

# Function to check number is a prime or not
def is_prime(num):
count = 0
for i in range(1,num+1):
if num % i is 0:
count += 1
if count is 2:
return 1
else:
return 0

# Driver Function
is_circular_prime("199")

RELATED TAGS

circular
prime
algorithm 