A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2885904 can be evenly divided by 1 2 3 4 6 7 8 9 12 14 16 18 21 24 28 36 42 48 49 56 63 72 84 98 112 126 144 147 168 196 252 294 336 392 409 441 504 588 784 818 882 1,008 1,176 1,227 1,636 1,764 2,352 2,454 2,863 3,272 3,528 3,681 4,908 5,726 6,544 7,056 7,362 8,589 9,816 11,452 14,724 17,178 19,632 20,041 22,904 25,767 29,448 34,356 40,082 45,808 51,534 58,896 60,123 68,712 80,164 103,068 120,246 137,424 160,328 180,369 206,136 240,492 320,656 360,738 412,272 480,984 721,476 961,968 1,442,952 and 2,885,904, with no remainder.
Since 2,885,904 cannot be divided by just 1 and 2,885,904, it is not a prime number.