A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2542500 can be evenly divided by 1 2 3 4 5 6 9 10 12 15 18 20 25 30 36 45 50 60 75 90 100 113 125 150 180 225 226 250 300 339 375 450 452 500 565 625 678 750 900 1,017 1,125 1,130 1,250 1,356 1,500 1,695 1,875 2,034 2,250 2,260 2,500 2,825 3,390 3,750 4,068 4,500 5,085 5,625 5,650 6,780 7,500 8,475 10,170 11,250 11,300 14,125 16,950 20,340 22,500 25,425 28,250 33,900 42,375 50,850 56,500 70,625 84,750 101,700 127,125 141,250 169,500 211,875 254,250 282,500 423,750 508,500 635,625 847,500 1,271,250 and 2,542,500, with no remainder.
Since 2,542,500 cannot be divided by just 1 and 2,542,500, it is not a prime number.