A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3388896 can be evenly divided by 1 2 3 4 6 7 8 9 12 14 16 18 21 24 28 32 36 41 42 48 56 63 72 82 84 96 112 123 126 144 164 168 224 246 252 287 288 328 336 369 492 504 574 656 672 738 861 984 1,008 1,148 1,312 1,476 1,681 1,722 1,968 2,016 2,296 2,583 2,952 3,362 3,444 3,936 4,592 5,043 5,166 5,904 6,724 6,888 9,184 10,086 10,332 11,767 11,808 13,448 13,776 15,129 20,172 20,664 23,534 26,896 27,552 30,258 35,301 40,344 41,328 47,068 53,792 60,516 70,602 80,688 82,656 94,136 105,903 121,032 141,204 161,376 188,272 211,806 242,064 282,408 376,544 423,612 484,128 564,816 847,224 1,129,632 1,694,448 and 3,388,896, with no remainder.
Since 3,388,896 cannot be divided by just 1 and 3,388,896, it is not a prime number.