# Solution Exercise 756 : algorithm python to find the largest prim number

Sep 17, 2020

#### Exercise 756

Write a Python algorithm as a function that takes an integer n as argument and returns the largest prime integer less than or equal to n. Example for n = 15, the function returns the largest prime number less than or equal to 15 which is 13.

#### Solution

``# creating function to test if given number is prim or notdef testPrim(m):    # Initializing number of divisors    numberDivisors = 0        # while i is divisor of m we increment numberDivisors    for i in range(1 , m + 1):        if(m%i == 0):            numberDivisors = numberDivisors + 1                # a number is prime if and only if it has two divisors, 1 and itself    if (numberDivisors == 2):        return True    else:        return False    def greatestPrim(n):    # initializing value of searched smallest prim p    p = n    while ( not testPrim(p) ):        p = p - 1    return p# Testing algorithmprint("The geatest prim less than or equal 15 is : " , greatestPrim(15))# The output is : The geatest prim less than or equal 15 is :  13``

Younes Derfoufi
my-courses.net