A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1845984 can be evenly divided by 1 2 3 4 6 7 8 12 14 16 21 24 28 32 41 42 48 56 67 82 84 96 112 123 134 164 168 201 224 246 268 287 328 336 402 469 492 536 574 656 672 804 861 938 984 1,072 1,148 1,312 1,407 1,608 1,722 1,876 1,968 2,144 2,296 2,747 2,814 3,216 3,444 3,752 3,936 4,592 5,494 5,628 6,432 6,888 7,504 8,241 9,184 10,988 11,256 13,776 15,008 16,482 19,229 21,976 22,512 27,552 32,964 38,458 43,952 45,024 57,687 65,928 76,916 87,904 115,374 131,856 153,832 230,748 263,712 307,664 461,496 615,328 922,992 and 1,845,984, with no remainder.
Since 1,845,984 cannot be divided by just 1 and 1,845,984, it is not a prime number.