It has been pointed out that the preamble instruction in Whodunnit? by Moog is imprecise. The statement 'Factors and multiples are non-trivial' does NOT apply to 16ac.
The clue for 16ac should read
'The population of the village which has 20 factors including 1 and itself'
Apologies for this oversight and the frustration that it has caused. We hope it hasn't detracted from your enjoyment of the puzzle.
It should be noted that in Pandigital Products by Oyler the clues for 13dn and 18dn should read
13dn it has 6 factors including 1 and itself.
18dn it has 10 factors including 1 and itself.