A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 4043088 can be evenly divided by 1 2 3 4 6 7 8 9 12 14 16 18 21 24 27 28 36 42 48 49 54 56 63 72 84 98 108 112 126 144 147 168 189 191 196 216 252 294 336 378 382 392 432 441 504 573 588 756 764 784 882 1,008 1,146 1,176 1,323 1,337 1,512 1,528 1,719 1,764 2,292 2,352 2,646 2,674 3,024 3,056 3,438 3,528 4,011 4,584 5,157 5,292 5,348 6,876 7,056 8,022 9,168 9,359 10,314 10,584 10,696 12,033 13,752 16,044 18,718 20,628 21,168 21,392 24,066 27,504 28,077 32,088 36,099 37,436 41,256 48,132 56,154 64,176 72,198 74,872 82,512 84,231 96,264 112,308 144,396 149,744 168,462 192,528 224,616 252,693 288,792 336,924 449,232 505,386 577,584 673,848 1,010,772 1,347,696 2,021,544 and 4,043,088, with no remainder.
Since 4,043,088 cannot be divided by just 1 and 4,043,088, it is not a prime number.