It's not very natural to use spaces instead of commas in English. I assume you mean 1,306,493.345? One million, three hundred and six thousand, four hundred and ninety three point three four five. Americans will say it slightly differently - possibly omitting some of the 'and's.

1 306 493.345 One million,three hundred and six thousand,four hundred and ninety-three point tree hundred and forty -five; One thousand thousand,three hundred and six thousand,four hundred and ninety-three point tree hundred and fourty-five;