Is there a power of 666 such that its decimal notation starts with the digits 123456789?
One may replace "starts" by "ends" for a much easier challenge ;-)
Absolutely!
Solve 666^x = 123456789.
It is not an integer, but 666 raised to the xth power both begins and ends with 123456789.
Or Solve for 666^y = 1234567890123456789.
Or solve 666^z = 123456789..anynumbers you choose..123456789