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by Brian Gladman on November 6, 2016

Sunday Times Teaser 2824 – New Extension

by Danny Roth

Published: 6 November 2016 (link)

George has just moved departments and he has a new four-figure telephone extension number. He shows it to Martha and proudly points out that, if you delete any two of the digits of the extension number, then the remaining two-figure number is prime. Martha then lists the resulting six different primes and comments delightedly that more than one of them divides exactly into the extension number.

What is George’s new extension number?

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