A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1729800 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 18 20 24 25 30 31 36 40 45 50 60 62 72 75 90 93 100 120 124 150 155 180 186 200 225 248 279 300 310 360 372 450 465 558 600 620 744 775 900 930 961 1,116 1,240 1,395 1,550 1,800 1,860 1,922 2,232 2,325 2,790 2,883 3,100 3,720 3,844 4,650 4,805 5,580 5,766 6,200 6,975 7,688 8,649 9,300 9,610 11,160 11,532 13,950 14,415 17,298 18,600 19,220 23,064 24,025 27,900 28,830 34,596 38,440 43,245 48,050 55,800 57,660 69,192 72,075 86,490 96,100 115,320 144,150 172,980 192,200 216,225 288,300 345,960 432,450 576,600 864,900 and 1,729,800, with no remainder.
Since 1,729,800 cannot be divided by just 1 and 1,729,800, it is not a prime number.