How to do this problem please guide me

#1

i am not able to think of a better logic other than to store sum of divisions of n with prime numbers…

#2

use inclusion and exclusion principle
like
count numbers divided by 2,3,7,11,13,17,19;
then subracts number divided by 23 ans 25 and 2*7 ans so on…
and then add all triples and subracts quadruples and so on…
for better explaination refer prateek bhaiya video