HR Red John is back

https://www.hackerrank.com/contests/101july13/challenges/red-john-is-back

Easy solution with the little dp and prime with very mild constraints

UVA 10717 Mint

Simple Prime number problem with sieve involved. Else part is brute force. Learn to use brute force seeing limits.

UVA10539 Almost Prime Numbers

Another easy one for prime number. Here u have to deal with the figures
after getting all primes just brute force . the no will be not large so u can afford it.
the exponential function grows very fast therefore no of almost prime are less(within computation limits)

UVA543 Goldbach's Conjecture

It is easy problem related to prime number
use sieve of erotheses

Prime problems

Learn about prime number from any standard book or competitive programming book.then  try to code basic algorithms like sieve for finding prime then try KPRIME,PRIME1,LEVY,PPERM,RESQ on codechef these are very simple and interesting problem and also their editorial is avalable . So,that u can surely learn something. I will add some other problem title related in somedays.