Question 431479
None of the factors can be greater than 1/2 of 42,
except for 1 x 42, so start with {{{42/2 = 21}}}
21 x 2 = 42 
Is 3 a factor? yes
14 x 3 = 42
4 and 5 are not factors, but
both 6 and 7 are
6 x 7 = 42
8 through 13 are not
15 through 20 are not
The factors are
1,2,3,6,7,14, and 21