Positive divisors of #120# are factors of #120#.
In number #120#, sum of digits is #3#, a multiple of #3#, hence it is divisible by #3#.
As last digit is #0#, it is also divisible by #2# and #5# (and also #10#.
The last two digits being #20#, it is also divisible by #4#.
Hence, some factors are #2#, #3#, #4# and #5#. As #2# and #3# are coprime too, it is divisible by #6# too. Similarly, it is also divisible by #10# (as #2# and #5# are coprime), #12# (as #3# and #4# are coprime),and #15# too (as #3# and #5# are coprime). As dividing by #4# we get, #30# which is even, #8# can also divide it.
Working similarly further, we can get divisors of #120# as
#{1,2,3,4,5,6,8,10,12,15,20,30,60,120}#
