import math


def compute_factors(n):
    """
    Return a list of all factors (proper divisors) of a number n, including the factor 1
    """
    factors = [1]
    for i in range(2, int(math.sqrt(n)) + 1):
        if n % i == 0:
            factors.append(i)
            factors.append(n // i)

    return factors