A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3286440 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 17 18 20 24 27 30 34 36 40 45 51 54 60 68 72 85 90 102 108 120 135 136 153 170 179 180 204 216 255 270 306 340 358 360 408 459 510 537 540 612 680 716 765 895 918 1,020 1,074 1,080 1,224 1,432 1,530 1,611 1,790 1,836 2,040 2,148 2,295 2,685 3,043 3,060 3,222 3,580 3,672 4,296 4,590 4,833 5,370 6,086 6,120 6,444 7,160 8,055 9,129 9,180 9,666 10,740 12,172 12,888 15,215 16,110 18,258 18,360 19,332 21,480 24,165 24,344 27,387 30,430 32,220 36,516 38,664 45,645 48,330 54,774 60,860 64,440 73,032 82,161 91,290 96,660 109,548 121,720 136,935 164,322 182,580 193,320 219,096 273,870 328,644 365,160 410,805 547,740 657,288 821,610 1,095,480 1,643,220 and 3,286,440, with no remainder.
Since 3,286,440 cannot be divided by just 1 and 3,286,440, it is not a prime number.