A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6866496 can be evenly divided by 1 2 3 4 6 7 8 9 12 13 14 16 18 21 24 26 28 32 36 39 42 48 52 56 63 64 72 78 84 91 96 104 112 117 126 131 144 156 168 182 192 208 224 234 252 262 273 288 312 336 364 393 416 448 468 504 524 546 576 624 672 728 786 819 832 917 936 1,008 1,048 1,092 1,179 1,248 1,344 1,456 1,572 1,638 1,703 1,834 1,872 2,016 2,096 2,184 2,358 2,496 2,751 2,912 3,144 3,276 3,406 3,668 3,744 4,032 4,192 4,368 4,716 5,109 5,502 5,824 6,288 6,552 6,812 7,336 7,488 8,253 8,384 8,736 9,432 10,218 11,004 11,921 12,576 13,104 13,624 14,672 15,327 16,506 17,472 18,864 20,436 22,008 23,842 25,152 26,208 27,248 29,344 30,654 33,012 35,763 37,728 40,872 44,016 47,684 52,416 54,496 58,688 61,308 66,024 71,526 75,456 81,744 88,032 95,368 107,289 108,992 122,616 132,048 143,052 163,488 176,064 190,736 214,578 245,232 264,096 286,104 326,976 381,472 429,156 490,464 528,192 572,208 762,944 858,312 980,928 1,144,416 1,716,624 2,288,832 3,433,248 and 6,866,496, with no remainder.
Since 6,866,496 cannot be divided by just 1 and 6,866,496, it is not a prime number.