This algorithm checks if a given positive integer number is prime or not. If it is, then returns a $\mathtt{True}$, otherwise $\mathtt{False}$.

#!/usr/bin/env python3
 
import math
 
def is_prime(n):
    if (n < 2) or (n % 2 == 0):
        return False
    elif n == 2 or n == 3:
        return True
 
    k = int(math.sqrt(n))
    for i in range(3, k+1, 2):
        if n % i == 0:
            return False
    return True

Example:

print(is_prime(127493299))

gives $\mathtt{True}$.

print(is_prime(127493285))

gives $\mathtt{False}$.