One of the most salient aspects of the discipline of number theory is that from a very small number of definitions, entities and axioms one is led to an extraordinary wealth and diversity of theorems, relations and problems–some of which can be easily stated yet are so complex that they take centuries of concerted efforts by the best mathematicians to find a proof (Fermat’s Last Theorem, …), or have resisted such efforts (Goldbach’s Conjecture, distribution of primes, …), or lead to mathematical entities of astounding complexity, or required extraordinary collective effort, or have been characterized by Paul Erdös as “Mathematics is not ready for such problems” (Collatz Conjecture).