A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1872450 can be evenly divided by 1 2 3 5 6 9 10 15 18 19 25 27 30 38 45 50 54 57 73 75 90 95 114 135 146 150 171 190 219 225 270 285 342 365 438 450 475 513 570 657 675 730 855 950 1,026 1,095 1,314 1,350 1,387 1,425 1,710 1,825 1,971 2,190 2,565 2,774 2,850 3,285 3,650 3,942 4,161 4,275 5,130 5,475 6,570 6,935 8,322 8,550 9,855 10,950 12,483 12,825 13,870 16,425 19,710 20,805 24,966 25,650 32,850 34,675 37,449 41,610 49,275 62,415 69,350 74,898 98,550 104,025 124,830 187,245 208,050 312,075 374,490 624,150 936,225 and 1,872,450, with no remainder.
Since 1,872,450 cannot be divided by just 1 and 1,872,450, it is not a prime number.