A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2639000 can be evenly divided by 1 2 4 5 7 8 10 13 14 20 25 26 28 29 35 40 50 52 56 58 65 70 91 100 104 116 125 130 140 145 175 182 200 203 232 250 260 280 290 325 350 364 377 406 455 500 520 580 650 700 725 728 754 812 875 910 1,000 1,015 1,160 1,300 1,400 1,450 1,508 1,624 1,625 1,750 1,820 1,885 2,030 2,275 2,600 2,639 2,900 3,016 3,250 3,500 3,625 3,640 3,770 4,060 4,550 5,075 5,278 5,800 6,500 7,000 7,250 7,540 8,120 9,100 9,425 10,150 10,556 11,375 13,000 13,195 14,500 15,080 18,200 18,850 20,300 21,112 22,750 25,375 26,390 29,000 37,700 40,600 45,500 47,125 50,750 52,780 65,975 75,400 91,000 94,250 101,500 105,560 131,950 188,500 203,000 263,900 329,875 377,000 527,800 659,750 1,319,500 and 2,639,000, with no remainder.
Since 2,639,000 cannot be divided by just 1 and 2,639,000, it is not a prime number.