A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 8148672 can be evenly divided by 1 2 3 4 6 7 8 9 12 14 16 18 21 24 28 32 36 42 43 47 48 56 63 64 72 84 86 94 96 112 126 129 141 144 168 172 188 192 224 252 258 282 288 301 329 336 344 376 387 423 448 504 516 564 576 602 658 672 688 752 774 846 903 987 1,008 1,032 1,128 1,204 1,316 1,344 1,376 1,504 1,548 1,692 1,806 1,974 2,016 2,021 2,064 2,256 2,408 2,632 2,709 2,752 2,961 3,008 3,096 3,384 3,612 3,948 4,032 4,042 4,128 4,512 4,816 5,264 5,418 5,922 6,063 6,192 6,768 7,224 7,896 8,084 8,256 9,024 9,632 10,528 10,836 11,844 12,126 12,384 13,536 14,147 14,448 15,792 16,168 18,189 19,264 21,056 21,672 23,688 24,252 24,768 27,072 28,294 28,896 31,584 32,336 36,378 42,441 43,344 47,376 48,504 56,588 57,792 63,168 64,672 72,756 84,882 86,688 94,752 97,008 113,176 127,323 129,344 145,512 169,764 173,376 189,504 194,016 226,352 254,646 291,024 339,528 388,032 452,704 509,292 582,048 679,056 905,408 1,018,584 1,164,096 1,358,112 2,037,168 2,716,224 4,074,336 and 8,148,672, with no remainder.
Since 8,148,672 cannot be divided by just 1 and 8,148,672, it is not a prime number.