A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 6475590 can be evenly divided by 1 2 3 5 6 9 10 11 15 18 22 30 31 33 45 55 62 66 90 93 99 110 155 165 186 198 211 279 310 330 341 422 465 495 558 633 682 930 990 1,023 1,055 1,266 1,395 1,705 1,899 2,046 2,110 2,321 2,790 3,069 3,165 3,410 3,798 4,642 5,115 6,138 6,330 6,541 6,963 9,495 10,230 11,605 13,082 13,926 15,345 18,990 19,623 20,889 23,210 30,690 32,705 34,815 39,246 41,778 58,869 65,410 69,630 71,951 98,115 104,445 117,738 143,902 196,230 208,890 215,853 294,345 359,755 431,706 588,690 647,559 719,510 1,079,265 1,295,118 2,158,530 3,237,795 and 6,475,590, with no remainder.
Since 6,475,590 cannot be divided by just 1 and 6,475,590, it is not a prime number.