A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1418616 can be evenly divided by 1 2 3 4 6 8 9 12 17 18 19 24 34 36 38 51 57 61 68 72 76 102 114 122 136 152 153 171 183 204 228 244 306 323 342 366 408 456 488 549 612 646 684 732 969 1,037 1,098 1,159 1,224 1,292 1,368 1,464 1,938 2,074 2,196 2,318 2,584 2,907 3,111 3,477 3,876 4,148 4,392 4,636 5,814 6,222 6,954 7,752 8,296 9,272 9,333 10,431 11,628 12,444 13,908 18,666 19,703 20,862 23,256 24,888 27,816 37,332 39,406 41,724 59,109 74,664 78,812 83,448 118,218 157,624 177,327 236,436 354,654 472,872 709,308 and 1,418,616, with no remainder.
Since 1,418,616 cannot be divided by just 1 and 1,418,616, it is not a prime number.