Input: An integer number greater than or equal to 2.
Output: True if the number is prime, False otherwise.
Steps:
1. If the input number is less than 2, return False (since prime numbers are greater than 1).
2. If the input number is 2, return True (since 2 is the only even prime number).
3. If the input number is even (divisible by 2), return False (excluding 2).
4. Loop from i starting from 3 up to the square root of number (inclusive), with a step size of 2 (to skip even divisors).
a. Check if number is divisible by i.
- If it is divisible, return False, as the number is not prime.
5. If the loop completes without finding any divisors, return True, as the number is prime.
Note: In the algorithm, we only need to check divisors up to the square root of the number because if there is a divisor greater than the square root, there must be a corresponding divisor smaller than the square root.
Pseudocode:
function is_prime(number):
if number < 2:
return False
if number == 2:
return True
if number % 2 == 0:
return False
for i in range(3, int(sqrt(number)) + 1, 2):
if number % i == 0:
return False
return True
