A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1868832 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 81 84 96 103 108 112 126 144 162 168 189 206 216 224 252 288 309 324 336 378 412 432 504 567 618 648 672 721 756 824 864 927 1,008 1,134 1,236 1,296 1,442 1,512 1,648 1,854 2,016 2,163 2,268 2,472 2,592 2,781 2,884 3,024 3,296 3,708 4,326 4,536 4,944 5,562 5,768 6,048 6,489 7,416 8,343 8,652 9,072 9,888 11,124 11,536 12,978 14,832 16,686 17,304 18,144 19,467 22,248 23,072 25,956 29,664 33,372 34,608 38,934 44,496 51,912 58,401 66,744 69,216 77,868 88,992 103,824 116,802 133,488 155,736 207,648 233,604 266,976 311,472 467,208 622,944 934,416 and 1,868,832, with no remainder.
Since 1,868,832 cannot be divided by just 1 and 1,868,832, it is not a prime number.