A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6411744 can be evenly divided by 1 2 3 4 6 8 9 12 16 18 24 27 32 36 41 48 54 72 82 96 108 123 144 164 181 216 246 288 328 362 369 432 492 543 656 724 738 864 984 1,086 1,107 1,312 1,448 1,476 1,629 1,968 2,172 2,214 2,896 2,952 3,258 3,936 4,344 4,428 4,887 5,792 5,904 6,516 7,421 8,688 8,856 9,774 11,808 13,032 14,842 17,376 17,712 19,548 22,263 26,064 29,684 35,424 39,096 44,526 52,128 59,368 66,789 78,192 89,052 118,736 133,578 156,384 178,104 200,367 237,472 267,156 356,208 400,734 534,312 712,416 801,468 1,068,624 1,602,936 2,137,248 3,205,872 and 6,411,744, with no remainder.
Since 6,411,744 cannot be divided by just 1 and 6,411,744, it is not a prime number.