A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2176680 can be evenly divided by 1 2 3 4 5 6 8 10 11 12 15 17 20 22 24 30 33 34 40 44 51 55 60 66 68 85 88 97 102 110 120 132 136 165 170 187 194 204 220 255 264 291 330 340 374 388 408 440 485 510 561 582 660 680 748 776 935 970 1,020 1,067 1,122 1,164 1,320 1,455 1,496 1,649 1,870 1,940 2,040 2,134 2,244 2,328 2,805 2,910 3,201 3,298 3,740 3,880 4,268 4,488 4,947 5,335 5,610 5,820 6,402 6,596 7,480 8,245 8,536 9,894 10,670 11,220 11,640 12,804 13,192 16,005 16,490 18,139 19,788 21,340 22,440 24,735 25,608 32,010 32,980 36,278 39,576 42,680 49,470 54,417 64,020 65,960 72,556 90,695 98,940 108,834 128,040 145,112 181,390 197,880 217,668 272,085 362,780 435,336 544,170 725,560 1,088,340 and 2,176,680, with no remainder.
Since 2,176,680 cannot be divided by just 1 and 2,176,680, it is not a prime number.