A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2510220 can be evenly divided by 1 2 3 4 5 6 10 12 15 17 20 23 30 34 46 51 60 68 69 85 92 102 107 115 138 170 204 214 230 255 276 321 340 345 391 428 460 510 535 642 690 782 1,020 1,070 1,173 1,284 1,380 1,564 1,605 1,819 1,955 2,140 2,346 2,461 3,210 3,638 3,910 4,692 4,922 5,457 5,865 6,420 7,276 7,383 7,820 9,095 9,844 10,914 11,730 12,305 14,766 18,190 21,828 23,460 24,610 27,285 29,532 36,380 36,915 41,837 49,220 54,570 73,830 83,674 109,140 125,511 147,660 167,348 209,185 251,022 418,370 502,044 627,555 836,740 1,255,110 and 2,510,220, with no remainder.
Since 2,510,220 cannot be divided by just 1 and 2,510,220, it is not a prime number.