I studied some number theory basic topics and after that I found some topics in some Youtube playlists such as:
- Euler totient
- Möbius inversion
- Chinese remainder theorem
- Diophantine equation
- Linear/segmented sieve
- Miller Rabin primality testing
- etc.
Are these topics really important and frequent in problems with rates $$$<1800$$$ and worth time or it's just a waste of time to learn them now?
