Prime numbers are the multiplicative building blocks of the integers. In this Woody Calculus lesson, learn the formal definition of a prime, why 1 is excluded, the Fundamental Theorem of Arithmetic, Euclid’s proof of infinitely many primes, the Sieve of Eratosthenes, prime patterns modulo 6, the Prime Number Theorem, modern cryptography, and the deep connection between primes and the Riemann Hypothesis.