A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6807240 can be evenly divided by 1 2 3 4 5 6 8 9 10 11 12 15 18 20 22 24 27 30 33 36 40 44 45 54 55 60 66 72 81 88 90 99 108 110 120 132 135 162 165 180 191 198 216 220 264 270 297 324 330 360 382 396 405 440 495 540 573 594 648 660 764 792 810 891 955 990 1,080 1,146 1,188 1,320 1,485 1,528 1,620 1,719 1,782 1,910 1,980 2,101 2,292 2,376 2,865 2,970 3,240 3,438 3,564 3,820 3,960 4,202 4,455 4,584 5,157 5,730 5,940 6,303 6,876 7,128 7,640 8,404 8,595 8,910 10,314 10,505 11,460 11,880 12,606 13,752 15,471 16,808 17,190 17,820 18,909 20,628 21,010 22,920 25,212 25,785 30,942 31,515 34,380 35,640 37,818 41,256 42,020 50,424 51,570 56,727 61,884 63,030 68,760 75,636 77,355 84,040 94,545 103,140 113,454 123,768 126,060 151,272 154,710 170,181 189,090 206,280 226,908 252,120 283,635 309,420 340,362 378,180 453,816 567,270 618,840 680,724 756,360 850,905 1,134,540 1,361,448 1,701,810 2,269,080 3,403,620 and 6,807,240, with no remainder.
Since 6,807,240 cannot be divided by just 1 and 6,807,240, it is not a prime number.