A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2001888 can be evenly divided by 1 2 3 4 6 7 8 9 12 14 16 18 21 24 27 28 32 36 42 48 54 56 63 72 84 96 108 112 126 144 168 189 216 224 252 288 331 336 378 432 504 662 672 756 864 993 1,008 1,324 1,512 1,986 2,016 2,317 2,648 2,979 3,024 3,972 4,634 5,296 5,958 6,048 6,951 7,944 8,937 9,268 10,592 11,916 13,902 15,888 17,874 18,536 20,853 23,832 27,804 31,776 35,748 37,072 41,706 47,664 55,608 62,559 71,496 74,144 83,412 95,328 111,216 125,118 142,992 166,824 222,432 250,236 285,984 333,648 500,472 667,296 1,000,944 and 2,001,888, with no remainder.
Since 2,001,888 cannot be divided by just 1 and 2,001,888, it is not a prime number.