A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3506412 can be evenly divided by 1 2 3 4 6 7 12 13 14 19 21 26 28 38 39 42 52 57 76 78 84 91 114 133 156 169 182 228 247 266 273 338 364 399 494 507 532 546 676 741 798 988 1,014 1,092 1,183 1,482 1,596 1,729 2,028 2,197 2,366 2,964 3,211 3,458 3,549 4,394 4,732 5,187 6,422 6,591 6,916 7,098 8,788 9,633 10,374 12,844 13,182 14,196 15,379 19,266 20,748 22,477 26,364 30,758 38,532 41,743 44,954 46,137 61,516 67,431 83,486 89,908 92,274 125,229 134,862 166,972 184,548 250,458 269,724 292,201 500,916 584,402 876,603 1,168,804 1,753,206 and 3,506,412, with no remainder.
Since 3,506,412 cannot be divided by just 1 and 3,506,412, it is not a prime number.