A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6501510 can be evenly divided by 1 2 3 5 6 9 10 15 18 29 30 45 47 53 58 87 90 94 106 141 145 159 174 235 261 265 282 290 318 423 435 470 477 522 530 705 795 846 870 954 1,305 1,363 1,410 1,537 1,590 2,115 2,385 2,491 2,610 2,726 3,074 4,089 4,230 4,611 4,770 4,982 6,815 7,473 7,685 8,178 9,222 12,267 12,455 13,630 13,833 14,946 15,370 20,445 22,419 23,055 24,534 24,910 27,666 37,365 40,890 44,838 46,110 61,335 69,165 72,239 74,730 112,095 122,670 138,330 144,478 216,717 224,190 361,195 433,434 650,151 722,390 1,083,585 1,300,302 2,167,170 3,250,755 and 6,501,510, with no remainder.
Since 6,501,510 cannot be divided by just 1 and 6,501,510, it is not a prime number.