A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3864336 can be evenly divided by 1 2 3 4 6 7 8 12 14 16 21 24 28 31 42 48 49 53 56 62 84 93 98 106 112 124 147 159 168 186 196 212 217 248 294 318 336 371 372 392 424 434 496 588 636 651 742 744 784 848 868 1,113 1,176 1,272 1,302 1,484 1,488 1,519 1,643 1,736 2,226 2,352 2,544 2,597 2,604 2,968 3,038 3,286 3,472 4,452 4,557 4,929 5,194 5,208 5,936 6,076 6,572 7,791 8,904 9,114 9,858 10,388 10,416 11,501 12,152 13,144 15,582 17,808 18,228 19,716 20,776 23,002 24,304 26,288 31,164 34,503 36,456 39,432 41,552 46,004 62,328 69,006 72,912 78,864 80,507 92,008 124,656 138,012 161,014 184,016 241,521 276,024 322,028 483,042 552,048 644,056 966,084 1,288,112 1,932,168 and 3,864,336, with no remainder.
Since 3,864,336 cannot be divided by just 1 and 3,864,336, it is not a prime number.