8888
This number is a composite.
The sum of the first 8888 primes is 386848087. Note the four 8's. [Blanchette]
8888 can be expressed as the sum of two consecutive primes (4441 + 4447). [De Geest]
81 + 80 + 83 + 83 = 1033, the concatenated exponents. [De Geest]
The only four-digit repdigit such that the product of itself and all truncations of itself plus one is prime, i.e., 8888*888*88*8 + 1 is prime. [Opao]
The only four-digit repdigit such that the sum of
itself and all truncations of itself minus one, i.e.,
8888+888+88+8 - 1 = 9871 is an emirp. [Bajpai]
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