A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2859516 can be evenly divided by 1 2 3 4 6 9 11 12 18 22 27 29 33 36 44 54 58 66 83 87 99 108 116 132 166 174 198 249 261 297 319 332 348 396 498 522 594 638 747 783 913 957 996 1,044 1,188 1,276 1,494 1,566 1,826 1,914 2,241 2,407 2,739 2,871 2,988 3,132 3,652 3,828 4,482 4,814 5,478 5,742 7,221 8,217 8,613 8,964 9,628 10,956 11,484 14,442 16,434 17,226 21,663 24,651 26,477 28,884 32,868 34,452 43,326 49,302 52,954 64,989 79,431 86,652 98,604 105,908 129,978 158,862 238,293 259,956 317,724 476,586 714,879 953,172 1,429,758 and 2,859,516, with no remainder.
Since 2,859,516 cannot be divided by just 1 and 2,859,516, it is not a prime number.