A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 836400 can be evenly divided by 1 2 3 4 5 6 8 10 12 15 16 17 20 24 25 30 34 40 41 48 50 51 60 68 75 80 82 85 100 102 120 123 136 150 164 170 200 204 205 240 246 255 272 300 328 340 400 408 410 425 492 510 600 615 656 680 697 816 820 850 984 1,020 1,025 1,200 1,230 1,275 1,360 1,394 1,640 1,700 1,968 2,040 2,050 2,091 2,460 2,550 2,788 3,075 3,280 3,400 3,485 4,080 4,100 4,182 4,920 5,100 5,576 6,150 6,800 6,970 8,200 8,364 9,840 10,200 10,455 11,152 12,300 13,940 16,400 16,728 17,425 20,400 20,910 24,600 27,880 33,456 34,850 41,820 49,200 52,275 55,760 69,700 83,640 104,550 139,400 167,280 209,100 278,800 418,200 and 836,400, with no remainder.
Since 836,400 cannot be divided by just 1 and 836,400, it is not a prime number.