A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 8646183 can be evenly divided by 1 3 7 9 13 17 21 23 27 39 51 63 69 81 91 117 119 153 161 189 207 221 243 273 299 351 357 391 459 483 567 621 663 819 897 1,053 1,071 1,173 1,377 1,449 1,547 1,701 1,863 1,989 2,093 2,457 2,691 2,737 3,159 3,213 3,519 4,131 4,347 4,641 5,083 5,589 5,967 6,279 7,371 8,073 8,211 9,639 10,557 13,041 13,923 15,249 17,901 18,837 22,113 24,219 24,633 28,917 31,671 35,581 39,123 41,769 45,747 53,703 56,511 72,657 73,899 95,013 106,743 125,307 137,241 169,533 221,697 320,229 375,921 411,723 508,599 665,091 960,687 1,235,169 2,882,061 and 8,646,183, with no remainder.
Since 8,646,183 cannot be divided by just 1 and 8,646,183, it is not a prime number.