A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 8722560 can be evenly divided by 1 2 3 4 5 6 7 8 10 11 12 14 15 16 20 21 22 24 28 30 32 33 35 40 42 44 48 55 56 59 60 64 66 70 77 80 84 88 96 105 110 112 118 120 128 132 140 154 160 165 168 176 177 192 210 220 224 231 236 240 264 280 295 308 320 330 336 352 354 384 385 413 420 440 448 462 472 480 528 560 590 616 640 649 660 672 704 708 770 826 840 880 885 896 924 944 960 1,056 1,120 1,155 1,180 1,232 1,239 1,298 1,320 1,344 1,408 1,416 1,540 1,652 1,680 1,760 1,770 1,848 1,888 1,920 1,947 2,065 2,112 2,240 2,310 2,360 2,464 2,478 2,596 2,640 2,688 2,832 3,080 3,245 3,304 3,360 3,520 3,540 3,696 3,776 3,894 4,130 4,224 4,480 4,543 4,620 4,720 4,928 4,956 5,192 5,280 5,664 6,160 6,195 6,490 6,608 6,720 7,040 7,080 7,392 7,552 7,788 8,260 9,086 9,240 9,440 9,735 9,856 9,912 10,384 10,560 11,328 12,320 12,390 12,980 13,216 13,440 13,629 14,160 14,784 15,576 16,520 18,172 18,480 18,880 19,470 19,824 20,768 21,120 22,656 22,715 24,640 24,780 25,960 26,432 27,258 28,320 29,568 31,152 33,040 36,344 36,960 37,760 38,940 39,648 41,536 45,430 49,280 49,560 51,920 52,864 54,516 56,640 62,304 66,080 68,145 72,688 73,920 77,880 79,296 83,072 90,860 99,120 103,840 109,032 113,280 124,608 132,160 136,290 145,376 147,840 155,760 158,592 181,720 198,240 207,680 218,064 249,216 264,320 272,580 290,752 311,520 363,440 396,480 415,360 436,128 545,160 581,504 623,040 726,880 792,960 872,256 1,090,320 1,246,080 1,453,760 1,744,512 2,180,640 2,907,520 4,361,280 and 8,722,560, with no remainder.
Since 8,722,560 cannot be divided by just 1 and 8,722,560, it is not a prime number.