Find the number N_max from the interval [60000, 1000000] that has the highest strength among all numbers in the interval

strength.py

#!/usr/bin/env python3

from functools import reduce
from multiprocessing import Pool
from operator import itemgetter


def factors(n):
    return set(reduce(list.__add__,
                      ([i, n//i] for i in range(1, int(n**0.5) + 1)
                       if not n % i)))


def strength(N):
    s = sum(factors(N))
    return(N, s/N)


if __name__ == "__main__":
    with Pool(4) as p:
        numbers = range(60000, 1000000)
        strengths = p.map(strength, numbers)
    (N, s) = max(strengths, key=itemgetter(1))
    print(f"N = {N}")
    print(f"Factors = {factors(N)}")
    print(f"Strength = {s}")