A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1264800 can be evenly divided by 1 2 3 4 5 6 8 10 12 15 16 17 20 24 25 30 31 32 34 40 48 50 51 60 62 68 75 80 85 93 96 100 102 120 124 136 150 155 160 170 186 200 204 240 248 255 272 300 310 340 372 400 408 425 465 480 496 510 527 544 600 620 680 744 775 800 816 850 930 992 1,020 1,054 1,200 1,240 1,275 1,360 1,488 1,550 1,581 1,632 1,700 1,860 2,040 2,108 2,325 2,400 2,480 2,550 2,635 2,720 2,976 3,100 3,162 3,400 3,720 4,080 4,216 4,650 4,960 5,100 5,270 6,200 6,324 6,800 7,440 7,905 8,160 8,432 9,300 10,200 10,540 12,400 12,648 13,175 13,600 14,880 15,810 16,864 18,600 20,400 21,080 24,800 25,296 26,350 31,620 37,200 39,525 40,800 42,160 50,592 52,700 63,240 74,400 79,050 84,320 105,400 126,480 158,100 210,800 252,960 316,200 421,600 632,400 and 1,264,800, with no remainder.
Since 1,264,800 cannot be divided by just 1 and 1,264,800, it is not a prime number.