10000...00001 (243-digits)
This number is a probable-prime (likely to be a prime but we have not (re-)proven it on this site).
100 0000000000 0000000000 0000000000
0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000000
0000000000 0000000777 0000000000 0000000000 0000000000 0000000000 0000000000
0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000001
The largest known Seraph prime. Metin Sariyar of Turkey reports no new Seraph primes up to 40,000 digits. [Qiita]
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