A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3168288 can be evenly divided by 1 2 3 4 6 8 9 12 16 18 19 24 27 32 36 38 48 54 57 72 76 96 108 114 144 152 171 193 216 228 288 304 342 386 432 456 513 579 608 684 772 864 912 1,026 1,158 1,368 1,544 1,737 1,824 2,052 2,316 2,736 3,088 3,474 3,667 4,104 4,632 5,211 5,472 6,176 6,948 7,334 8,208 9,264 10,422 11,001 13,896 14,668 16,416 18,528 20,844 22,002 27,792 29,336 33,003 41,688 44,004 55,584 58,672 66,006 83,376 88,008 99,009 117,344 132,012 166,752 176,016 198,018 264,024 352,032 396,036 528,048 792,072 1,056,096 1,584,144 and 3,168,288, with no remainder.
Since 3,168,288 cannot be divided by just 1 and 3,168,288, it is not a prime number.