Enigma 1701: Lit up
From New Scientist #2868, 9th June 2012 [link]
The display on my calculator shows 9876543210.
As usual, up to seven illuminated strips are used to display each digit – the 8 using all seven, for example. There is just one special 10-figure number with the property that it is a perfect power of the total number of illuminated strips that it uses.
With a little calculator effort it is possible to answer the following: How many illuminated strips does this special 10-figure number use?