The book is now available! 7
(another Prime Pages' Curiosity)
Prime Curios!
Curios: Curios Search:

Single Curio View:   (Seek other curios for this number)


Divisibility test for 7 (or 13): Combine the digits in order into groups of 3 (starting from the right) by alternating them with positive and negative signs. If the result is divisible by 7 (or 13 respectively), then so is the original number. For example, 7 divides 62540982 because 7 divides +(62)-(540)+(982).


  Submitted: 2008-09-05 11:19:07;   Last Modified: 2008-09-05 11:22:02.

Prime Curios! © 2000-2018 (all rights reserved)  privacy statement