Turn this prime number upside down to get the year of the Norman Conquest of England.
9901, 99990001, 999999000001, and 9999999900000001, are primes. [Avrutin]
The greatest prime factor of any 12-digit repdigit is 9901. [La Haye]
A prime whose square (98029801) is the concatenation of two consecutive numbers in descending order. [Bopardikar]
The only known prime with reciprocal of period dozen. [Post]
(There is one curio for this number that has not yet been approved by an editor.)
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