A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 797040 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 16 18 20 24 27 30 36 40 41 45 48 54 60 72 80 81 82 90 108 120 123 135 144 162 164 180 205 216 240 243 246 270 324 328 360 369 405 410 432 486 492 540 615 648 656 720 738 810 820 972 984 1,080 1,107 1,215 1,230 1,296 1,476 1,620 1,640 1,845 1,944 1,968 2,160 2,214 2,430 2,460 2,952 3,240 3,280 3,321 3,690 3,888 4,428 4,860 4,920 5,535 5,904 6,480 6,642 7,380 8,856 9,720 9,840 9,963 11,070 13,284 14,760 16,605 17,712 19,440 19,926 22,140 26,568 29,520 33,210 39,852 44,280 49,815 53,136 66,420 79,704 88,560 99,630 132,840 159,408 199,260 265,680 398,520 and 797,040, with no remainder.
Since 797,040 cannot be divided by just 1 and 797,040, it is not a prime number.