1,238,926,361,552,897

Number
$1 \, 238 \, 926 \, 361 \, 552 \, 897$ is:


 * The $n$th prime, where $n$ remains to be determined


 * One of the two prime factors of the $9$th Fermat number $2^{\left({2^8}\right)} + 1$:
 * $1 \, 238 \, 926 \, 361 \, 552 \, 897 = 1 \, 209 \, 889 \, 024 \, 954 \times 2^{10} + 1$