A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2629800 can be evenly divided by 1 2 3 4 5 6 8 9 10 12 15 18 20 24 25 27 30 36 40 45 50 54 60 72 75 90 100 108 120 135 150 180 200 216 225 270 300 360 450 487 540 600 675 900 974 1,080 1,350 1,461 1,800 1,948 2,435 2,700 2,922 3,896 4,383 4,870 5,400 5,844 7,305 8,766 9,740 11,688 12,175 13,149 14,610 17,532 19,480 21,915 24,350 26,298 29,220 35,064 36,525 43,830 48,700 52,596 58,440 65,745 73,050 87,660 97,400 105,192 109,575 131,490 146,100 175,320 219,150 262,980 292,200 328,725 438,300 525,960 657,450 876,600 1,314,900 and 2,629,800, with no remainder.
Since 2,629,800 cannot be divided by just 1 and 2,629,800, it is not a prime number.