Ans: 689
There are six non-prime digits -0, 1,4,6,8,&9.: : Zero cannot be a part of a 3 digit number whose digits are in strictly ascending order: So there are ten combinations of three-digit numbers with digits in ascending order using the 5 digits -1,4,6,8, and 9:
146, 148, 149, 168, 169, 189, 468, 469, 489, 689:
Of these, four are even. : This leaves:
149, 169, 189, 469, 489, 689:
149 is prime, therefore has no prime divisors.:
169 = 13*13 so the two divisors are not distinct:
189 = 3³ * 7, cannot form two prime divisors.:
489 = 3 * 163, no two- digit divisors. :
This leaves 689 = 13 * 53
:

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