I know that "los dos sabemos" (ambos sabemos) mean "we both know". Similarly, "los tres sabemos" - "we three know".
But when definite article is used before numbers in other cases? As for me, more frequently I encounter only "definite article + noun" or "number + noun (and no definite article)". But below are different examples, for which I would ask you to explain why definite article is used:
1) "los 380 flying fortress" - this was referring to 380 Flying Fortress planes (from movie about World War 2).
2) From article regarding 9/11 in Wiki, in the first paragraph (https://es.wikipedia.org/wiki/Atentados_del_11_de_septiembre_de_2001): "«11S», fueron una serie de cuatro atentados terroristas suicidas cometidos la mañana del martes 11 de septiembre de 2001 en los Estados Unidos por la red yihadista Al Qaeda que mediante el secuestro de aviones comerciales para ser impactados contra diversos objetivos causaron la muerte de 3016 personas, incluidos LOS diecinueve terroristas."
Here, why "los" is used for "19 terroristas", but not used before "3016 personas"? My guess - in case of terrorists it is used to state that all 19 of them died (similar to "los dos sabemos" example), but I would use word "todos" before "los 19" to emphasize this.