[seqfan] Re: Numbers with 3 divisors

Christopher Gribble chris.eveswell at virgin.net
Thu Aug 18 14:01:53 CEST 2011

A number with exactly 3 divisors can only be the square of a prime.
Apart from primes 2 and 5, all other primes end in 1, 3, 7 or 9, so their
squares end in 1 or 9.

Best regards,

Chris Gribble

-----Original Message-----
From: seqfan-bounces at list.seqfan.eu [mailto:seqfan-bounces at list.seqfan.eu]
On Behalf Of Harvey P. Dale
Sent: 18 August 2011 12:42 PM
To: seqfan at seqfan.eu
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




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