A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 4288896 can be evenly divided by 1 2 3 4 6 8 9 12 16 17 18 24 27 32 34 36 48 51 54 64 68 72 73 96 102 108 128 136 144 146 153 192 204 216 219 272 288 292 306 384 408 432 438 459 544 576 584 612 657 816 864 876 918 1,088 1,152 1,168 1,224 1,241 1,314 1,632 1,728 1,752 1,836 1,971 2,176 2,336 2,448 2,482 2,628 3,264 3,456 3,504 3,672 3,723 3,942 4,672 4,896 4,964 5,256 6,528 7,008 7,344 7,446 7,884 9,344 9,792 9,928 10,512 11,169 14,016 14,688 14,892 15,768 19,584 19,856 21,024 22,338 28,032 29,376 29,784 31,536 33,507 39,712 42,048 44,676 58,752 59,568 63,072 67,014 79,424 84,096 89,352 119,136 126,144 134,028 158,848 178,704 238,272 252,288 268,056 357,408 476,544 536,112 714,816 1,072,224 1,429,632 2,144,448 and 4,288,896, with no remainder.
Since 4,288,896 cannot be divided by just 1 and 4,288,896, it is not a prime number.