Learn and practice: Numbers in Spanish. 3

Millions
Integer multiples of a million, used as counters of things, are always accompanied by the preposition “de“; for example: “tres millones de euros.” When amounts less than a million are specified, within the same number, this preposition is not used, for example: “tres millones quinientos mil euros”
The multiples of a million are always masculine: it is said “quinientos millones de personas” even though “persona” is feminine and “quinientos” can be used in feminine. However, it is said “quinientos millones quinientas mil personas.”
The following table shows the standard usage in Spanish, which uses the long scale:

1 000 mil
1 000 000 un millón
2 000 000 dos millones
500 000 000 quinientos millones
1 000 000 000 mil millones (
sometimes «un millardo»)
1 200 000 000 mil doscientos millones
5 000 000 000 cinco mil millones
1 000 000 000 000 un billón
1 000 000 000 000 000 mil billones
1 000 000 000 000 000 000 un trillón
1 000 000 000 000 000 000 000 000 un cuatrillón

Sometimes a decimal number is used to multiply to a million or the power of a million. It is also used for “millardos”, despite being very rare in Spanish.

1 200 000 un millón doscientos (doscientas) mil : uno coma dos millones (=1,2 millones)
1 200 000 000 mil doscientos millones: uno coma dos millardos (=1,2 millardos)
1 200 000 000 000 un billón doscientos mil millones: uno coma dos billones (=1,2 billones)