A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3286400 can be evenly divided by 1 2 4 5 8 10 13 16 20 25 26 32 40 50 52 64 65 79 80 100 104 128 130 158 160 200 208 260 316 320 325 395 400 416 520 632 640 650 790 800 832 1,027 1,040 1,264 1,300 1,580 1,600 1,664 1,975 2,054 2,080 2,528 2,600 3,160 3,200 3,950 4,108 4,160 5,056 5,135 5,200 6,320 7,900 8,216 8,320 10,112 10,270 10,400 12,640 15,800 16,432 20,540 20,800 25,280 25,675 31,600 32,864 41,080 41,600 50,560 51,350 63,200 65,728 82,160 102,700 126,400 131,456 164,320 205,400 252,800 328,640 410,800 657,280 821,600 1,643,200 and 3,286,400, with no remainder.
Since 3,286,400 cannot be divided by just 1 and 3,286,400, it is not a prime number.