A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 7880040 can be evenly divided by 1 2 3 4 5 6 7 8 9 10 12 14 15 18 20 21 24 28 30 35 36 40 42 45 53 56 59 60 63 70 72 84 90 105 106 118 120 126 140 159 168 177 180 210 212 236 252 265 280 295 315 318 354 360 371 413 420 424 472 477 504 530 531 590 630 636 708 742 795 826 840 885 954 1,060 1,062 1,113 1,180 1,239 1,260 1,272 1,416 1,484 1,590 1,652 1,770 1,855 1,908 2,065 2,120 2,124 2,226 2,360 2,385 2,478 2,520 2,655 2,968 3,127 3,180 3,304 3,339 3,540 3,710 3,717 3,816 4,130 4,248 4,452 4,770 4,956 5,310 5,565 6,195 6,254 6,360 6,678 7,080 7,420 7,434 8,260 8,904 9,381 9,540 9,912 10,620 11,130 12,390 12,508 13,356 14,840 14,868 15,635 16,520 16,695 18,585 18,762 19,080 21,240 21,889 22,260 24,780 25,016 26,712 28,143 29,736 31,270 33,390 37,170 37,524 43,778 44,520 46,905 49,560 56,286 62,540 65,667 66,780 74,340 75,048 87,556 93,810 109,445 112,572 125,080 131,334 133,560 140,715 148,680 175,112 187,620 197,001 218,890 225,144 262,668 281,430 328,335 375,240 394,002 437,780 525,336 562,860 656,670 788,004 875,560 985,005 1,125,720 1,313,340 1,576,008 1,970,010 2,626,680 3,940,020 and 7,880,040, with no remainder.
Since 7,880,040 cannot be divided by just 1 and 7,880,040, it is not a prime number.