A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2840040 can be evenly divided by 1 2 3 4 5 6 7 8 9 10 12 14 15 18 20 21 23 24 28 30 35 36 40 42 45 46 49 56 60 63 69 70 72 84 90 92 98 105 115 120 126 138 140 147 161 168 180 184 196 207 210 230 245 252 276 280 294 315 322 343 345 360 392 414 420 441 460 483 490 504 552 588 630 644 686 690 735 805 828 840 882 920 966 980 1,029 1,035 1,127 1,176 1,260 1,288 1,372 1,380 1,449 1,470 1,610 1,656 1,715 1,764 1,932 1,960 2,058 2,070 2,205 2,254 2,415 2,520 2,744 2,760 2,898 2,940 3,087 3,220 3,381 3,430 3,528 3,864 4,116 4,140 4,410 4,508 4,830 5,145 5,635 5,796 5,880 6,174 6,440 6,762 6,860 7,245 7,889 8,232 8,280 8,820 9,016 9,660 10,143 10,290 11,270 11,592 12,348 13,524 13,720 14,490 15,435 15,778 16,905 17,640 19,320 20,286 20,580 22,540 23,667 24,696 27,048 28,980 30,870 31,556 33,810 39,445 40,572 41,160 45,080 47,334 50,715 57,960 61,740 63,112 67,620 71,001 78,890 81,144 94,668 101,430 118,335 123,480 135,240 142,002 157,780 189,336 202,860 236,670 284,004 315,560 355,005 405,720 473,340 568,008 710,010 946,680 1,420,020 and 2,840,040, with no remainder.
Since 2,840,040 cannot be divided by just 1 and 2,840,040, it is not a prime number.