A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 1564272 can be evenly divided by 1 2 3 4 6 8 9 12 16 17 18 24 27 34 36 48 51 54 68 71 72 81 102 108 136 142 144 153 162 204 213 216 272 284 306 324 408 426 432 459 568 612 639 648 816 852 918 1,136 1,207 1,224 1,278 1,296 1,377 1,704 1,836 1,917 2,414 2,448 2,556 2,754 3,408 3,621 3,672 3,834 4,828 5,112 5,508 5,751 7,242 7,344 7,668 9,656 10,224 10,863 11,016 11,502 14,484 15,336 19,312 21,726 22,032 23,004 28,968 30,672 32,589 43,452 46,008 57,936 65,178 86,904 92,016 97,767 130,356 173,808 195,534 260,712 391,068 521,424 782,136 and 1,564,272, with no remainder.
Since 1,564,272 cannot be divided by just 1 and 1,564,272, it is not a prime number.