A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3953040 can be evenly divided by 1 2 3 4 5 6 7 8 10 12 13 14 15 16 20 21 24 26 28 30 35 39 40 42 48 52 56 60 65 70 78 80 84 91 104 105 112 120 130 140 156 168 181 182 195 208 210 240 260 273 280 312 336 362 364 390 420 455 520 543 546 560 624 724 728 780 840 905 910 1,040 1,086 1,092 1,267 1,365 1,448 1,456 1,560 1,680 1,810 1,820 2,172 2,184 2,353 2,534 2,715 2,730 2,896 3,120 3,620 3,640 3,801 4,344 4,368 4,706 5,068 5,430 5,460 6,335 7,059 7,240 7,280 7,602 8,688 9,412 10,136 10,860 10,920 11,765 12,670 14,118 14,480 15,204 16,471 18,824 19,005 20,272 21,720 21,840 23,530 25,340 28,236 30,408 32,942 35,295 37,648 38,010 43,440 47,060 49,413 50,680 56,472 60,816 65,884 70,590 76,020 82,355 94,120 98,826 101,360 112,944 131,768 141,180 152,040 164,710 188,240 197,652 247,065 263,536 282,360 304,080 329,420 395,304 494,130 564,720 658,840 790,608 988,260 1,317,680 1,976,520 and 3,953,040, with no remainder.
Since 3,953,040 cannot be divided by just 1 and 3,953,040, it is not a prime number.