A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3538290 can be evenly divided by 1 2 3 5 6 7 10 14 15 21 29 30 35 42 49 58 70 83 87 98 105 145 147 166 174 203 210 245 249 290 294 406 415 435 490 498 581 609 735 830 870 1,015 1,162 1,218 1,245 1,421 1,470 1,743 2,030 2,407 2,490 2,842 2,905 3,045 3,486 4,067 4,263 4,814 5,810 6,090 7,105 7,221 8,134 8,526 8,715 12,035 12,201 14,210 14,442 16,849 17,430 20,335 21,315 24,070 24,402 33,698 36,105 40,670 42,630 50,547 61,005 72,210 84,245 101,094 117,943 122,010 168,490 235,886 252,735 353,829 505,470 589,715 707,658 1,179,430 1,769,145 and 3,538,290, with no remainder.
Since 3,538,290 cannot be divided by just 1 and 3,538,290, it is not a prime number.