A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6620670 can be evenly divided by 1 2 3 5 6 7 9 10 14 15 18 21 27 30 31 35 42 45 54 62 63 70 90 93 105 113 126 135 155 186 189 210 217 226 270 279 310 315 339 378 434 465 558 565 630 651 678 791 837 930 945 1,017 1,085 1,130 1,302 1,395 1,582 1,674 1,695 1,890 1,953 2,034 2,170 2,373 2,790 3,051 3,255 3,390 3,503 3,906 3,955 4,185 4,746 5,085 5,859 6,102 6,510 7,006 7,119 7,910 8,370 9,765 10,170 10,509 11,718 11,865 14,238 15,255 17,515 19,530 21,018 21,357 23,730 24,521 29,295 30,510 31,527 35,030 35,595 42,714 49,042 52,545 58,590 63,054 71,190 73,563 94,581 105,090 106,785 122,605 147,126 157,635 189,162 213,570 220,689 245,210 315,270 367,815 441,378 472,905 662,067 735,630 945,810 1,103,445 1,324,134 2,206,890 3,310,335 and 6,620,670, with no remainder.
Since 6,620,670 cannot be divided by just 1 and 6,620,670, it is not a prime number.