A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 8589120 can be evenly divided by 1 2 3 4 5 6 8 10 12 15 16 20 23 24 30 32 40 46 48 60 64 69 80 92 96 115 120 138 160 184 192 230 240 276 320 345 368 389 460 480 552 690 736 778 920 960 1,104 1,167 1,380 1,472 1,556 1,840 1,945 2,208 2,334 2,760 3,112 3,680 3,890 4,416 4,668 5,520 5,835 6,224 7,360 7,780 8,947 9,336 11,040 11,670 12,448 15,560 17,894 18,672 22,080 23,340 24,896 26,841 31,120 35,788 37,344 44,735 46,680 53,682 62,240 71,576 74,688 89,470 93,360 107,364 124,480 134,205 143,152 178,940 186,720 214,728 268,410 286,304 357,880 373,440 429,456 536,820 572,608 715,760 858,912 1,073,640 1,431,520 1,717,824 2,147,280 2,863,040 4,294,560 and 8,589,120, with no remainder.
Since 8,589,120 cannot be divided by just 1 and 8,589,120, it is not a prime number.