Did I read the problem wrong? Isn’t this problem asking me to find out the smallest prime and odd factor of the number N/5? I am pretty sure about the ans(hint: ans is >3 and <13) but it is showing wrong. And now i don’t have the chance to test even as this is a contest problem and gz doesn’t take answer on contest problems.
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I also think so. The answer should be 5. Here’s how I figured it out:
N=2020²⁰²⁰ + 25
N/5 = (2020²⁰²⁰ + 25)/5
= (2020²⁰¹⁹ × 2020 + 5 × 5)/5
= (2020²⁰¹⁸ × 2020 × 404 + 5)
= 5(2020²⁰¹⁸ × 404² + 1)
Therefore, dividing N/5 with 5 results (2020²⁰¹⁸ × 404² + 1). So the least odd prime divisor should be 5.
yeah,I also tried to solve it in this way…But 5 isn’t correct,the correct answer is 13; according to Gonitzoggo…
how is that, did you find out?
no ! 
I actually submitted 5,3,7,11 & 13; one after another…and 13 was the correct answer …
I also find the answer with this process. Luckily there is no submission limit. 