A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3051594 can be evenly divided by 1 2 3 6 7 9 13 14 18 21 23 26 27 39 42 46 54 63 69 78 81 91 117 126 138 161 162 182 189 207 234 243 273 299 322 351 378 414 483 486 546 567 598 621 702 729 819 897 966 1,053 1,134 1,242 1,449 1,458 1,638 1,701 1,794 1,863 2,093 2,106 2,457 2,691 2,898 3,159 3,402 3,726 4,186 4,347 4,914 5,103 5,382 5,589 6,279 6,318 7,371 8,073 8,694 9,477 10,206 11,178 12,558 13,041 14,742 16,146 16,767 18,837 18,954 22,113 24,219 26,082 33,534 37,674 39,123 44,226 48,438 56,511 66,339 72,657 78,246 113,022 117,369 132,678 145,314 169,533 217,971 234,738 339,066 435,942 508,599 1,017,198 1,525,797 and 3,051,594, with no remainder.
Since 3,051,594 cannot be divided by just 1 and 3,051,594, it is not a prime number.