A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6307308 can be evenly divided by 1 2 3 4 6 7 9 12 14 18 21 27 28 36 42 54 63 81 84 103 108 126 162 189 206 243 252 309 324 378 412 486 567 618 721 729 756 927 972 1,134 1,236 1,442 1,458 1,701 1,854 2,163 2,187 2,268 2,781 2,884 2,916 3,402 3,708 4,326 4,374 5,103 5,562 6,489 6,804 8,343 8,652 8,748 10,206 11,124 12,978 15,309 16,686 19,467 20,412 25,029 25,956 30,618 33,372 38,934 50,058 58,401 61,236 75,087 77,868 100,116 116,802 150,174 175,203 225,261 233,604 300,348 350,406 450,522 525,609 700,812 901,044 1,051,218 1,576,827 2,102,436 3,153,654 and 6,307,308, with no remainder.
Since 6,307,308 cannot be divided by just 1 and 6,307,308, it is not a prime number.