What number do I multiply by to give me 1,428 outof 1,2,6, and8.

2 answers

Divide 1,428 by each of those numbers. What do you get?
There are some short cuts:

1 will always work

since the number is even (ends in 8)
the number is divisible by 2.

If the sum of the digits is divisible by 3 then the number is divisible by 3.

If the number is divisible by 2 and 3 then it is divisible by 6.