A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3479490 can be evenly divided by 1 2 3 5 6 7 9 10 14 15 18 21 27 30 35 42 45 49 54 63 70 90 98 105 126 135 147 189 210 245 263 270 294 315 378 441 490 526 630 735 789 882 945 1,315 1,323 1,470 1,578 1,841 1,890 2,205 2,367 2,630 2,646 3,682 3,945 4,410 4,734 5,523 6,615 7,101 7,890 9,205 11,046 11,835 12,887 13,230 14,202 16,569 18,410 23,670 25,774 27,615 33,138 35,505 38,661 49,707 55,230 64,435 71,010 77,322 82,845 99,414 115,983 128,870 165,690 193,305 231,966 248,535 347,949 386,610 497,070 579,915 695,898 1,159,830 1,739,745 and 3,479,490, with no remainder.
Since 3,479,490 cannot be divided by just 1 and 3,479,490, it is not a prime number.