A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2004120 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 18 19 20 24 30 36 38 40 45 57 60 72 76 90 95 114 120 152 171 180 190 228 285 293 342 360 380 456 570 586 684 760 855 879 1,140 1,172 1,368 1,465 1,710 1,758 2,280 2,344 2,637 2,930 3,420 3,516 4,395 5,274 5,567 5,860 6,840 7,032 8,790 10,548 11,134 11,720 13,185 16,701 17,580 21,096 22,268 26,370 27,835 33,402 35,160 44,536 50,103 52,740 55,670 66,804 83,505 100,206 105,480 111,340 133,608 167,010 200,412 222,680 250,515 334,020 400,824 501,030 668,040 1,002,060 and 2,004,120, with no remainder.
Since 2,004,120 cannot be divided by just 1 and 2,004,120, it is not a prime number.