A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3661308 can be evenly divided by 1 2 3 4 6 7 9 12 14 18 21 27 28 29 36 42 54 58 63 84 87 108 116 126 167 174 189 203 252 261 334 348 378 406 501 522 609 668 756 783 812 1,002 1,044 1,169 1,218 1,503 1,566 1,827 2,004 2,338 2,436 3,006 3,132 3,507 3,654 4,509 4,676 4,843 5,481 6,012 7,014 7,308 9,018 9,686 10,521 10,962 14,028 14,529 18,036 19,372 21,042 21,924 29,058 31,563 33,901 42,084 43,587 58,116 63,126 67,802 87,174 101,703 126,252 130,761 135,604 174,348 203,406 261,522 305,109 406,812 523,044 610,218 915,327 1,220,436 1,830,654 and 3,661,308, with no remainder.
Since 3,661,308 cannot be divided by just 1 and 3,661,308, it is not a prime number.