A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6777600 can be evenly divided by 1 2 3 4 5 6 8 10 12 15 16 20 24 25 30 32 40 48 50 60 64 75 80 96 100 120 128 150 160 192 200 240 256 300 320 353 384 400 480 600 640 706 768 800 960 1,059 1,200 1,280 1,412 1,600 1,765 1,920 2,118 2,400 2,824 3,200 3,530 3,840 4,236 4,800 5,295 5,648 6,400 7,060 8,472 8,825 9,600 10,590 11,296 14,120 16,944 17,650 19,200 21,180 22,592 26,475 28,240 33,888 35,300 42,360 45,184 52,950 56,480 67,776 70,600 84,720 90,368 105,900 112,960 135,552 141,200 169,440 211,800 225,920 271,104 282,400 338,880 423,600 451,840 564,800 677,760 847,200 1,129,600 1,355,520 1,694,400 2,259,200 3,388,800 and 6,777,600, with no remainder.
Since 6,777,600 cannot be divided by just 1 and 6,777,600, it is not a prime number.