What are the possible values of a six digit positive integer N, where all digits of N are different, and 4*N has the same six digits as N?
Prove that there are no others.
(In reply to Let me count the ways
by Steve Herman)
Let Me REcount the ways:
.....So at first glance we have 12*8*7*6*5 = 20,160 possibilities.
But the number must equal 0 OR 3 OR 6 mod 9, because N and 4N have the same digits.
And approximately 1/3 of the 20,160 possibilities meet this criteria.
So I guess that there are only 6720 viable candidates for N...
see the sod of Charlie's numbers" :18,21,27 etc.