10000...00001 (181-digits)

This number is a probable-prime (likely to be a prime but we have not (re-)proven it on this site).

                               1 0000000000 0000000000 0000000000 0000000000
0000000000 0000000000 0000000000 0000000000 0000000008 0000000000 0000000000
0000000000 0000000000 0000000000 0000000000 0000000000 0000000000 0000000001

The only known tetradic prime of the form 100^n+8*10^n+1 containing a tetradic prime number of digits. Here, n = 90. [Honaker]