How would you say $1.7 billion in Spanish?pretty much how would you say any US currency amount in the billions in spanish?

The translation of billions and trillions from an English
language variety to a Spanish or other European language variety all depends on which
value for "billion" and "trillion" is used. Let me explain using
"billion."

Until recently, American English and British
English values for "billion" differed with the AE value being less and the BE value
being more. Oxford Dictionary says the higher BE value used
to be a "million million (i.e. 1,000,000,000,000)" while the lower AE
value was and still is a "thousand million (i.e. 1,000,000,000)." As I
said, BE has recently adopted the AE
value so now both these varieties of English use the lower
American value of a thousand million (i.e.
1,000,000,000).

European
languages show the same value differences that used to exist between AE
and BE: European languages, like Spain's Spanish, use the
higher value for a billion of a million million (i.e. 1,000,000,000,000) while
American English influenced Spanish varieties, like
American-Mexican Spanish, use the lower value of a thousand
million (i.e. 1,000,000,000).

If you count the
zeros to help keep it sorted, the higher value has 12 zeros
while the lower value has 9 zeros. So while Spain's Spanish
uses the 12 zero million million for 'billion" (as the UK used to do), it is possible
that North American varieties of Spanish may use the AE
influenced 9 zero thousand million for "billion."