A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1831800 can be evenly divided by 1 2 3 4 5 6 8 10 12 15 20 24 25 30 40 43 50 60 71 75 86 100 120 129 142 150 172 200 213 215 258 284 300 344 355 426 430 516 568 600 645 710 852 860 1,032 1,065 1,075 1,290 1,420 1,704 1,720 1,775 2,130 2,150 2,580 2,840 3,053 3,225 3,550 4,260 4,300 5,160 5,325 6,106 6,450 7,100 8,520 8,600 9,159 10,650 12,212 12,900 14,200 15,265 18,318 21,300 24,424 25,800 30,530 36,636 42,600 45,795 61,060 73,272 76,325 91,590 122,120 152,650 183,180 228,975 305,300 366,360 457,950 610,600 915,900 and 1,831,800, with no remainder.
Since 1,831,800 cannot be divided by just 1 and 1,831,800, it is not a prime number.