A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1629450 can be evenly divided by 1 2 3 5 6 9 10 15 17 18 25 27 30 34 45 50 51 54 71 75 85 90 102 135 142 150 153 170 213 225 255 270 306 355 425 426 450 459 510 639 675 710 765 850 918 1,065 1,207 1,275 1,278 1,350 1,530 1,775 1,917 2,130 2,295 2,414 2,550 3,195 3,550 3,621 3,825 3,834 4,590 5,325 6,035 6,390 7,242 7,650 9,585 10,650 10,863 11,475 12,070 15,975 18,105 19,170 21,726 22,950 30,175 31,950 32,589 36,210 47,925 54,315 60,350 65,178 90,525 95,850 108,630 162,945 181,050 271,575 325,890 543,150 814,725 and 1,629,450, with no remainder.
Since 1,629,450 cannot be divided by just 1 and 1,629,450, it is not a prime number.