# $$(XY+ YX )$$ % 7?

If the number 16 is added to its reverse, $$16+ 61= 77$$.
The sum is 77 which is divisible by 7.
But you will not find many numbers have this property.
For example $$15 + 51 = 66$$, which is not divisible by 7.
How many two digit-number has this properties?

Assume that $$05$$ is not a two-digit number.

×