A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3993120 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 16 18 20 24 30 32 36 40 45 47 48 59 60 72 80 90 94 96 118 120 141 144 160 177 180 188 235 236 240 282 288 295 354 360 376 423 470 472 480 531 564 590 705 708 720 752 846 885 940 944 1,062 1,128 1,180 1,410 1,416 1,440 1,504 1,692 1,770 1,880 1,888 2,115 2,124 2,256 2,360 2,655 2,773 2,820 2,832 3,384 3,540 3,760 4,230 4,248 4,512 4,720 5,310 5,546 5,640 5,664 6,768 7,080 7,520 8,319 8,460 8,496 9,440 10,620 11,092 11,280 13,536 13,865 14,160 16,638 16,920 16,992 21,240 22,184 22,560 24,957 27,730 28,320 33,276 33,840 41,595 42,480 44,368 49,914 55,460 66,552 67,680 83,190 84,960 88,736 99,828 110,920 124,785 133,104 166,380 199,656 221,840 249,570 266,208 332,760 399,312 443,680 499,140 665,520 798,624 998,280 1,331,040 1,996,560 and 3,993,120, with no remainder.
Since 3,993,120 cannot be divided by just 1 and 3,993,120, it is not a prime number.