#math trivia #159 solution

One of the primes must be less than or equal to the square root of 366, i.e., 19 or less.  We can enumerate the possibilities for the other prime, and thus the product, accordingly:

  • 3:  3 -> 9; 13 -> 39; 23 -> 69; 43 -> 129; 53 -> 159; 73 -> 219; 83 -> 249; 103 -> 309; 113 -> 349
  • 5:  5 -> 25
  • 7:  7 -> 49; 17 -> 119; 37 -> 259; 47 -> 329
  • 11:  11 -> 121; 31 -> 341
  • 13:  13 -> 169; 23 -> 299
  • 17:  17 -> 289

It’s interesting how many of these products have primes with the last digit of 3, and how few with 5.  Why is that?

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