Back in 1969 I was taking a number theory class, and I remember being taught that it was the purest of pure math subjects with (essentially) no application. It

Back in 1969 I was taking a number theory class, and I remember being taught that it was the purest of pure math subjects with (essentially) no application. It was simply a subject with beautiful results and beautiful proofs—good training for a budding mathematician. Ironically, now the results of number theory are an important foundation for essential computer science.