"¿Qué número es" translates to "What number is it?"

"Es el número..." means "It is the number...". We use this expression to answer the question: "¿Qué número es?"

"Es el número diez" means "It is the number ten".

"El número once" means "The number eleven".

"El número doce" means "The number twelve".

"El número trece" translates to "The number thirteen".

"El número catorce" means "The number fourteen".

"Es el número quince" stands for "It is the number fifteen".

"Es el número dieciseis" means "It is the number sixteen".

"El número diecisiete" translates to "The number seventeen".

"El número dieciocho" means "The number eighteen".

"El número diecinueve" stands for "The number nineteen".

Remember that ¿Qué número es? means What number is it? If you were shown the number twenty, your answers to this question would be Es el número veinte / It is the number twenty.