[seqfan] Re: Numbers with 3 divisors
mathstutoring at ntlworld.com
Thu Aug 18 14:02:09 CEST 2011
If a number has three divisors, it is necessarily the square of a prime.
And as these can only have units digits 1, 3, 7 or 9, their squares can only
terminate in 1 or 9.
----- Original Message -----
From: "Harvey P. Dale" <hpd1 at nyu.edu>
To: <seqfan at seqfan.eu>
Sent: Thursday, August 18, 2011 12:41 PM
Subject: [seqfan] Numbers with 3 divisors
> Is it true that all numbers with exactly three divisors,
> with the exception only of 4 and 25, have either 1 or 9 as their last
> decimal digit?
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