91av

Factory parts

The number 3120 is divisible without remainder by each number in the following set: 3, 312, 12, 120, 2 and 20. Each of these numbers will be called a visible proper divisor (VPD) of 3120 because each is visible either as a single digit or as a group of adjacent digits in 3120. (1 and 3120 have been excluded as being improper, in order that any prime number has no VPDs).

ENIGMA represents an odd six-digit number in which all the digits are different. The set of all VPDs of ENIGMA is E, NI, IG, G, GMA, M, MA, and A. What is ENIGMA?

WIN £15 will be awarded to the sender of the first correct answer opened on Tuesday 1 May. The Editor’s decision is final. Please send entries to Enigma 1691, 91av, Lacon House, 84 Theobald’s Road, London WC1X 8NS, or to enigma@newscientist.com (please include your postal address).

Answer to 1685 A noted eccentric: One or other of the clocks must have been read on a Tuesday

The winner Richard Crews of San Jose, California, US