A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6753240 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 13 15 18 20 24 26 27 30 36 37 39 40 45 52 54 60 65 72 74 78 90 104 108 111 117 120 130 135 148 156 169 180 185 195 216 222 234 260 270 296 312 333 338 351 360 370 390 444 468 481 507 520 540 555 585 666 676 702 740 780 845 888 936 962 999 1,014 1,080 1,110 1,170 1,332 1,352 1,404 1,443 1,480 1,521 1,560 1,665 1,690 1,755 1,924 1,998 2,028 2,220 2,340 2,405 2,535 2,664 2,808 2,886 3,042 3,330 3,380 3,510 3,848 3,996 4,056 4,329 4,440 4,563 4,680 4,810 4,995 5,070 5,772 6,084 6,253 6,660 6,760 7,020 7,215 7,605 7,992 8,658 9,126 9,620 9,990 10,140 11,544 12,168 12,506 12,987 13,320 14,040 14,430 15,210 17,316 18,252 18,759 19,240 19,980 20,280 21,645 22,815 25,012 25,974 28,860 30,420 31,265 34,632 36,504 37,518 39,960 43,290 45,630 50,024 51,948 56,277 57,720 60,840 62,530 64,935 75,036 86,580 91,260 93,795 103,896 112,554 125,060 129,870 150,072 168,831 173,160 182,520 187,590 225,108 250,120 259,740 281,385 337,662 375,180 450,216 519,480 562,770 675,324 750,360 844,155 1,125,540 1,350,648 1,688,310 2,251,080 3,376,620 and 6,753,240, with no remainder.
Since 6,753,240 cannot be divided by just 1 and 6,753,240, it is not a prime number.