818752171
This number is a prime.
The smallest prime p such that the numbers
21 + 31 + 51 + 71 + 111 + ... + p1,
22 + 32 + 52 + 72 + 112 + ... + p2,
23 + 33 + 53 + 73 + 113 + ... + p3,
24 + 34 + 54 + 74 + 114 + ... + p4,
25 + 35 + 55 + 75 + 115 + ... + p5,
are all primes. [Crespi de Valldaura]
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