A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 9866240 can be evenly divided by 1 2 4 5 8 10 16 20 32 40 41 47 64 80 82 94 128 160 164 188 205 235 256 320 328 376 410 470 512 640 656 752 820 940 1,024 1,280 1,312 1,504 1,640 1,880 1,927 2,560 2,624 3,008 3,280 3,760 3,854 5,120 5,248 6,016 6,560 7,520 7,708 9,635 10,496 12,032 13,120 15,040 15,416 19,270 20,992 24,064 26,240 30,080 30,832 38,540 41,984 48,128 52,480 60,160 61,664 77,080 104,960 120,320 123,328 154,160 209,920 240,640 246,656 308,320 493,312 616,640 986,624 1,233,280 1,973,248 2,466,560 4,933,120 and 9,866,240, with no remainder.
Since 9,866,240 cannot be divided by just 1 and 9,866,240, it is not a prime number.