This number is a prime.
The largest prime factor of any 28-digit repdigit. Note that 28 is perfect. [Bowser]
The largest prime (emirp) factor of 10^14+1. [Loungrides]
The largest prime factor, (it is also emirp), of any number
formed by repeating seven times any 4-digit number, (prime
or composite). [Loungrides]
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