A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2644992 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 64 72 82 84 96 112 123 126 128 144 164 168 192 224 246 252 256 287 288 328 336 369 384 448 492 504 512 574 576 656 672 738 768 861 896 984 1,008 1,024 1,148 1,152 1,312 1,344 1,476 1,536 1,722 1,792 1,968 2,016 2,296 2,304 2,583 2,624 2,688 2,952 3,072 3,444 3,584 3,936 4,032 4,592 4,608 5,166 5,248 5,376 5,904 6,888 7,168 7,872 8,064 9,184 9,216 10,332 10,496 10,752 11,808 13,776 15,744 16,128 18,368 20,664 20,992 21,504 23,616 27,552 31,488 32,256 36,736 41,328 41,984 47,232 55,104 62,976 64,512 73,472 82,656 94,464 110,208 125,952 146,944 165,312 188,928 220,416 293,888 330,624 377,856 440,832 661,248 881,664 1,322,496 and 2,644,992, with no remainder.
Since 2,644,992 cannot be divided by just 1 and 2,644,992, it is not a prime number.