The structure and underlying regularities of the apparently chaotic Collatz sequences are studied. Their stopping time, and their total stopping time, follow surprisingly simple formulas. The relationship with prime numbers and some famous theorems and unsolved problems are studied, such as Bertrand's postulate, de Polignac's conjecture. The twin prime conjecture is rephrased as an example of the pigeonhole principle. No attempt is made to prove the Collatz Conjecture, nor the Twin Prime Conjecture.weiterlesen