4,294,967,297

Number
$4 \, 294 \, 967 \, 297$ is:


 * $641 \times 6 \, 700 \, 417$


 * The $6$th Fermat number after $3$, $5$, $17$, $257$, $65 \, 537$:
 * $4 \, 294 \, 967 \, 297 = 2^{\paren {2^5} } + 1 = 2^{32} + 1$
 * and the $1$st not to be prime.

Also see

 * Prime Decomposition of 5th Fermat Number