[seqfan] Digital question

[David Wilson]

Let d > 0 divide 99. I can then show that d divides n iff d divides the base-10 reverse of n.

I believe the converse is true as well, that these are the only d with this property.

In general, I believe that

( d | n <=> d | base-b reverse of n ) <=> d | b^2-1

Supposing this is indeed true, it can't be too hard to prove, but I'm at a loss.


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