A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 766800 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 16 18 20 24 25 27 30 36 40 45 48 50 54 60 71 72 75 80 90 100 108 120 135 142 144 150 180 200 213 216 225 240 270 284 300 355 360 400 426 432 450 540 568 600 639 675 710 720 852 900 1,065 1,080 1,136 1,200 1,278 1,350 1,420 1,704 1,775 1,800 1,917 2,130 2,160 2,556 2,700 2,840 3,195 3,408 3,550 3,600 3,834 4,260 5,112 5,325 5,400 5,680 6,390 7,100 7,668 8,520 9,585 10,224 10,650 10,800 12,780 14,200 15,336 15,975 17,040 19,170 21,300 25,560 28,400 30,672 31,950 38,340 42,600 47,925 51,120 63,900 76,680 85,200 95,850 127,800 153,360 191,700 255,600 383,400 and 766,800, with no remainder.
Since 766,800 cannot be divided by just 1 and 766,800, it is not a prime number.