Prime numbers play an extremely important role in modern mathematics. Apart from still being the object of intense research activity, their applications in banking and security underline a key phenomenon: in the modern world, useful applications of mathematics often come from very "pure" abstract theories. Curiously, despite their undeniable importance, prime numbers are largely absent from school curricula. Prime numbers are typically encountered in Year 7. There one looks at the sieve of Eratosthenes, which students use to find the primes up to some limit, like 100. Another common thing to do at this age is to explore Goldbach's conjecture: that every even number greater than or equal to 4 is the sum of two primes. Students might be asked to find all pairs of primes that add up to 76, for example. Sadly, this is often the only material on primes that some students see in their entire school studies.