#order You wrote:

 if is_prime(divisor) and number % divisor == 0:

that is, if A and B:.

But B is typically false and is quickly computed. Prefer if B and A:

#stride Rather than

 for divisor in range(int(number ** 0.5) + 1, 0, -1):

you might want to begin with an odd number and then use a stride of -2. You needn't special case for when number is a power of two, since the input clearly isn't.

#sieve Consider sieving for the solution.

order

You wrote:

 if is_prime(divisor) and number % divisor == 0:

that is, if A and B:.

But B is typically false and is quickly computed. Prefer if B and A:

stride

Rather than

 for divisor in range(int(number ** 0.5) + 1, 0, -1):

you might want to begin with an odd number and then use a stride of -2. You needn't special case for when number is a power of two, since the input clearly isn't.

sieve

Consider sieving for the solution.