A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 3857100 can be evenly divided by 1 2 3 4 5 6 10 12 13 15 20 23 25 26 30 39 43 46 50 52 60 65 69 75 78 86 92 100 115 129 130 138 150 156 172 195 215 230 258 260 276 299 300 325 345 390 430 460 516 559 575 598 645 650 690 780 860 897 975 989 1,075 1,118 1,150 1,196 1,290 1,300 1,380 1,495 1,677 1,725 1,794 1,950 1,978 2,150 2,236 2,300 2,580 2,795 2,967 2,990 3,225 3,354 3,450 3,588 3,900 3,956 4,300 4,485 4,945 5,590 5,934 5,980 6,450 6,708 6,900 7,475 8,385 8,970 9,890 11,180 11,868 12,857 12,900 13,975 14,835 14,950 16,770 17,940 19,780 22,425 24,725 25,714 27,950 29,670 29,900 33,540 38,571 41,925 44,850 49,450 51,428 55,900 59,340 64,285 74,175 77,142 83,850 89,700 98,900 128,570 148,350 154,284 167,700 192,855 257,140 296,700 321,425 385,710 642,850 771,420 964,275 1,285,700 1,928,550 and 3,857,100, with no remainder.
Since 3,857,100 cannot be divided by just 1 and 3,857,100, it is not a prime number.