A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3858140 can be evenly divided by 1 2 4 5 10 11 13 19 20 22 26 38 44 52 55 65 71 76 95 110 130 142 143 190 209 220 247 260 284 286 355 380 418 494 572 710 715 781 836 923 988 1,045 1,235 1,349 1,420 1,430 1,562 1,846 2,090 2,470 2,698 2,717 2,860 3,124 3,692 3,905 4,180 4,615 4,940 5,396 5,434 6,745 7,810 9,230 10,153 10,868 13,490 13,585 14,839 15,620 17,537 18,460 20,306 26,980 27,170 29,678 35,074 40,612 50,765 54,340 59,356 70,148 74,195 87,685 101,530 148,390 175,370 192,907 203,060 296,780 350,740 385,814 771,628 964,535 1,929,070 and 3,858,140, with no remainder.
Since 3,858,140 cannot be divided by just 1 and 3,858,140, it is not a prime number.