30 Jul '06 02:57>3 edits
Originally posted by perihelion2006 = 2 * 17 * 59
And we have a winner!
For those still trying to figure it out, Bowmann's observation that most of them are composites is on the right track. Keep looking in this direction for something more specific.
351 = 3 * 3 * 3 * 13
378 = 2 * 3 * 3 * 3 * 7
386 = 2 * 193
428 = 2 * 2 * 107
463 is prime
So what?
Anyway, if factoring - and then manipulating the factors - of 25 numbers one-by-one is not trial and error, what do you call it? ('Boring' might be a good start.)