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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:

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.