title: Finding a prime number after a given number
body: <p>How can I find the least prime number greater than a given number?  For example, given 4, I need 5; given 7, I need 11.</p>
  
  <p>I would like to know some ideas on best algorithms to do this. One method that I thought of was generate primes numbers through the Sieve of Eratosthenes, and then find the prime after the given number.</p>