A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1625260 can be evenly divided by 1 2 4 5 7 10 13 14 19 20 26 28 35 38 47 52 65 70 76 91 94 95 130 133 140 182 188 190 235 247 260 266 329 364 380 455 470 494 532 611 658 665 893 910 940 988 1,222 1,235 1,316 1,330 1,645 1,729 1,786 1,820 2,444 2,470 2,660 3,055 3,290 3,458 3,572 4,277 4,465 4,940 6,110 6,251 6,580 6,916 8,554 8,645 8,930 11,609 12,220 12,502 17,108 17,290 17,860 21,385 23,218 25,004 31,255 34,580 42,770 46,436 58,045 62,510 81,263 85,540 116,090 125,020 162,526 232,180 325,052 406,315 812,630 and 1,625,260, with no remainder.
Since 1,625,260 cannot be divided by just 1 and 1,625,260, it is not a prime number.