Correct answer:
The number 657,666 is seiscientos cincuenta y siete mil seiscientos sesenta y seis in Spanish that means six hundred fifty-seven thousand six hundred sixty-six in English. So each digit represents something that we can write in Spanish in the following way:
6: Centena de mil
5: Decena de mil
7: Unidad de mil
6: Centena
6: Decena
6: Unidad