Immersion tip: Millions and billions
What English speakers write as 10 billion, Spanish speakers apparently prefer to write as 10.000 millones. That's using the period as a thousands separator rather than as a decimal point, so it would be rendered as 10,000 million in English. But people usually don't say 10,000 million in English, so translating it as 10 billion is preferable.
For the curious, the Spanish usage of "10.000 millones" is due to the Spanish-speaking world's use of the long scale number system (http://en.wikipedia.org/wiki/Long_and_short_scales). So you should also watch out that a Spanish "billón" is actually a trillion in English.
Thanks so much for including the Wikipedia link; it actually explains the logic behind each system which will make this all easier to remember.
Yes; in most of Europe the "." is the thousands separator and the comma is the decimal point.
When I'm writing long numbers in either language I often use a space as a thousands separator to try to reduce ambiguity.
9 732 343.45
For an American billion (1 000 000 000), we have the uncommon Spanish word 'millardo', but 'mil millones' is much more usual.
Sadly, UK media now all seem to use an American billion instead of a European one. (Though I personally think the press should use SI prefixes for large quantities of e.g. money - gigadollars, tetraeuros. But do they listen to me?)
And in English, when the long system was still in use, 1,000,000,000 was called a "milliard".