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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?
WIN £15 will be awarded to the sender of the first correct answer opened on Wednesday 11 July. The Editor’s decision is final. Please send entries to Enigma 1701, New ÐÓ°ÉÔ´´, Lacon House, 84 Theobald’s Road, London WC1X 8NS, or to enigma@newscientist.com (please include your postal address).
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Answer to 1695 Odd one out: 185
The winner K. H. Kirklin of London, UK