A divisor $ d $ satisfies $ d \equiv 1 \pmod4 $ if it is odd (so $ d $ not divisible by 2) and $ d \equiv 1 \pmod4 $. So restrict to odd divisors. Since $ d $ must be odd, we ignore the power of 2. So consider only divisors of $ 3^2 \cdot 5 = 45 $. - Veritas Home Health