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## Random mathematics factoid.

Well, sometimes I get five minutes off to goof around and I find silly facts, which as far as I can tell serve little to no purpose. Hence the name factoid is sometimes applied to them. The random novelty of the day is that the number

$1111111111111111111$

is prime. Moreover, it is a factor of $1010101010101010101010101010101010101$. The only other prime factor is almost as pretty.

$909090909090909091$

Beware  of $909090909090909090909090909091$ which surprise, surprise, it  also happens to be prime. And so seems to be

$11111111111111111111111$

If someone knows anything more about these primes, please let it be known. I found them by accident, but they seem to have been discovered before my time, so I can not name them after myself, nor get a patent for them.