A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 5751564 can be evenly divided by 1 2 3 4 6 7 12 13 14 21 23 26 28 39 42 46 52 69 78 84 91 92 138 156 161 182 229 273 276 299 322 364 458 483 546 598 644 687 897 916 966 1,092 1,196 1,374 1,603 1,794 1,932 2,093 2,748 2,977 3,206 3,588 4,186 4,809 5,267 5,954 6,279 6,412 8,372 8,931 9,618 10,534 11,908 12,558 15,801 17,862 19,236 20,839 21,068 25,116 31,602 35,724 36,869 41,678 62,517 63,204 68,471 73,738 83,356 110,607 125,034 136,942 147,476 205,413 221,214 250,068 273,884 410,826 442,428 479,297 821,652 958,594 1,437,891 1,917,188 2,875,782 and 5,751,564, with no remainder.
Since 5,751,564 cannot be divided by just 1 and 5,751,564, it is not a prime number.