A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 8006250 can be evenly divided by 1 2 3 5 6 7 10 14 15 21 25 30 35 42 50 61 70 75 105 122 125 150 175 183 210 250 305 350 366 375 427 525 610 625 750 854 875 915 1,050 1,250 1,281 1,525 1,750 1,830 1,875 2,135 2,562 2,625 3,050 3,125 3,750 4,270 4,375 4,575 5,250 6,250 6,405 7,625 8,750 9,150 9,375 10,675 12,810 13,125 15,250 18,750 21,350 21,875 22,875 26,250 32,025 38,125 43,750 45,750 53,375 64,050 65,625 76,250 106,750 114,375 131,250 160,125 190,625 228,750 266,875 320,250 381,250 533,750 571,875 800,625 1,143,750 1,334,375 1,601,250 2,668,750 4,003,125 and 8,006,250, with no remainder.
Since 8,006,250 cannot be divided by just 1 and 8,006,250, it is not a prime number.