A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 859680 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 16 18 20 24 27 30 32 36 40 45 48 54 60 72 80 90 96 108 120 135 144 160 180 199 216 240 270 288 360 398 432 480 540 597 720 796 864 995 1,080 1,194 1,440 1,592 1,791 1,990 2,160 2,388 2,985 3,184 3,582 3,980 4,320 4,776 5,373 5,970 6,368 7,164 7,960 8,955 9,552 10,746 11,940 14,328 15,920 17,910 19,104 21,492 23,880 26,865 28,656 31,840 35,820 42,984 47,760 53,730 57,312 71,640 85,968 95,520 107,460 143,280 171,936 214,920 286,560 429,840 and 859,680, with no remainder.
Since 859,680 cannot be divided by just 1 and 859,680, it is not a prime number.