340,282,366,920,938,463,463,374,607,431,768,211,457

Number
$340 \, 282 \, 366 \, 920 \, 938 \, 463 \, 463 \, 374 \, 607 \, 431 \, 768 \, 211 \, 457$ is:


 * $59 \, 649 \, 589 \, 127 \, 497 \, 217 \times 5 \, 704 \, 689 \, 200 \, 685 \, 129 \, 054 \, 721$


 * The $8$th Fermat number after $3$, $5$, $17$, $257$, $65 \, 537$, $4 \, 294 \, 967 \, 297$, $18 \, 446 \, 744 \, 073 \, 709 \, 551 \, 617$:
 * $340 \, 282 \, 366 \, 920 \, 938 \, 463 \, 463 \, 374 \, 607 \, 431 \, 768 \, 211 \, 457 = 2^{\left({2^7}\right)} + 1 = 2^{128} + 1$
 * and the $3$rd not to be prime.

Also see

 * Prime Decomposition of 8th Fermat Number