A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 986400 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 16 18 20 24 25 30 32 36 40 45 48 50 60 72 75 80 90 96 100 120 137 144 150 160 180 200 225 240 274 288 300 360 400 411 450 480 548 600 685 720 800 822 900 1,096 1,200 1,233 1,370 1,440 1,644 1,800 2,055 2,192 2,400 2,466 2,740 3,288 3,425 3,600 4,110 4,384 4,932 5,480 6,165 6,576 6,850 7,200 8,220 9,864 10,275 10,960 12,330 13,152 13,700 16,440 19,728 20,550 21,920 24,660 27,400 30,825 32,880 39,456 41,100 49,320 54,800 61,650 65,760 82,200 98,640 109,600 123,300 164,400 197,280 246,600 328,800 493,200 and 986,400, with no remainder.
Since 986,400 cannot be divided by just 1 and 986,400, it is not a prime number.