ABSTRACT
Peter started multiplying primes. He skipped the fi rst few because he knew they were too small.
11 × 11 = 121 13 × 13 = 169 17 × 17 = 289 19 × 19 = 361
“OK,” said Peter, “We see that 19 is the fi rst prime number whose square is greater than 343. By our rule, we only have to test primes less than 19 to see whether they are divisors of 343.” (This is Problem 1a.)
Jenny decided to try a larger number. “Is 1019 prime?” she wondered.
