1000 is the first - anything divisible by 20 whose digits do not add to a multiple of three works - so 1020 doesn't, but 1040 and 1060 do.
Also 2000.
The lowest 4-digit number that is divisible by 6 is 1002
1002 is the smallest 4 digit number divisible by 3 and 2.
There can be no such number.
1028
1000
7200 is one such number.
4444
3030
3030
The highest six-digit number divisible by 3, 4, and 5 is 999960.
9996
1234