Euler Project Problem #1
Before the review, let me advise you that Project Euler problems have very little to do with programming. They are mostly about math. Your code is very ineffective because it scales (almost) linearly with the range, whereas the solution can be achieved in a (almost) constant time.


The construct

    if condition:
        return True
    else
        return False


is a long way to say

    return condition

The in range loop which modifies its loop variable, as in

for nat_num_iterator in range(range_start, range_end):
    ....
    nat_num_iterator += 1


gives me shivers. Here you increment nat_num_iterator twice per iteration. If it is an intent, use range(range_start, range_end, 2).