A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1837224 can be evenly divided by 1 2 3 4 6 8 9 12 17 18 19 24 34 36 38 51 57 68 72 76 79 102 114 136 152 153 158 171 204 228 237 306 316 323 342 408 456 474 612 632 646 684 711 948 969 1,224 1,292 1,343 1,368 1,422 1,501 1,896 1,938 2,584 2,686 2,844 2,907 3,002 3,876 4,029 4,503 5,372 5,688 5,814 6,004 7,752 8,058 9,006 10,744 11,628 12,008 12,087 13,509 16,116 18,012 23,256 24,174 25,517 27,018 32,232 36,024 48,348 51,034 54,036 76,551 96,696 102,068 108,072 153,102 204,136 229,653 306,204 459,306 612,408 918,612 and 1,837,224, with no remainder.
Since 1,837,224 cannot be divided by just 1 and 1,837,224, it is not a prime number.