909091

+ The greatest prime factor of any 14-digit repdigit is 909091. [La Haye]

+ The only prime of period fourteen. Note that 909091 contains 9091, the only prime of period ten. [Beedassy]

+ 909091 is a factor of 1010101010101. [Pimentel]

+ The largest unique emirp. [Loungrides]

+ The largest prime factor, (emirp), of any number formed by repeating two times any 7-digit number or seven times any double-digit number. [Loungrides]

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