A prime number is a natural number, greater than one, that can only be divided by 1 and itself.
The number 2057748 can be evenly divided by 1 2 3 4 6 7 11 12 14 17 21 22 28 33 34 42 44 51 66 68 77 84 102 119 131 132 154 187 204 231 238 262 308 357 374 393 462 476 524 561 714 748 786 917 924 1,122 1,309 1,428 1,441 1,572 1,834 2,227 2,244 2,618 2,751 2,882 3,668 3,927 4,323 4,454 5,236 5,502 5,764 6,681 7,854 8,646 8,908 10,087 11,004 13,362 15,589 15,708 17,292 20,174 24,497 26,724 30,261 31,178 40,348 46,767 48,994 60,522 62,356 73,491 93,534 97,988 121,044 146,982 171,479 187,068 293,964 342,958 514,437 685,916 1,028,874 and 2,057,748, with no remainder.
Since 2,057,748 cannot be divided by just 1 and 2,057,748, it is not a prime number.