A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6908664 can be evenly divided by 1 2 3 4 6 7 8 12 14 17 21 24 28 34 41 42 51 56 59 68 82 84 102 118 119 123 136 164 168 177 204 236 238 246 287 328 354 357 408 413 472 476 492 574 697 708 714 826 861 952 984 1,003 1,148 1,239 1,394 1,416 1,428 1,652 1,722 2,006 2,091 2,296 2,419 2,478 2,788 2,856 3,009 3,304 3,444 4,012 4,182 4,838 4,879 4,956 5,576 6,018 6,888 7,021 7,257 8,024 8,364 9,676 9,758 9,912 12,036 14,042 14,514 14,637 16,728 16,933 19,352 19,516 21,063 24,072 28,084 29,028 29,274 33,866 39,032 41,123 42,126 50,799 56,168 58,056 58,548 67,732 82,246 84,252 101,598 117,096 123,369 135,464 164,492 168,504 203,196 246,738 287,861 328,984 406,392 493,476 575,722 863,583 986,952 1,151,444 1,727,166 2,302,888 3,454,332 and 6,908,664, with no remainder.
Since 6,908,664 cannot be divided by just 1 and 6,908,664, it is not a prime number.