A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 8460288 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 81 96 102 108 128 136 144 153 162 192 204 216 243 256 272 288 306 324 384 408 432 459 486 512 544 576 612 648 768 816 864 918 972 1,024 1,088 1,152 1,224 1,296 1,377 1,536 1,632 1,728 1,836 1,944 2,048 2,176 2,304 2,448 2,592 2,754 3,072 3,264 3,456 3,672 3,888 4,131 4,352 4,608 4,896 5,184 5,508 6,144 6,528 6,912 7,344 7,776 8,262 8,704 9,216 9,792 10,368 11,016 13,056 13,824 14,688 15,552 16,524 17,408 18,432 19,584 20,736 22,032 26,112 27,648 29,376 31,104 33,048 34,816 39,168 41,472 44,064 52,224 55,296 58,752 62,208 66,096 78,336 82,944 88,128 104,448 117,504 124,416 132,192 156,672 165,888 176,256 235,008 248,832 264,384 313,344 352,512 470,016 497,664 528,768 705,024 940,032 1,057,536 1,410,048 2,115,072 2,820,096 4,230,144 and 8,460,288, with no remainder.
Since 8,460,288 cannot be divided by just 1 and 8,460,288, it is not a prime number.