3,445 three thousand, four hundred (and) forty five
1,753 one thousand seven hundred (and) fifty three
2,003 two thousand (and) three
300,000 three hundred thousand
4,000,000 4 million
7,000,000,000 7 billion
5,809 five thousand eight hundred (and) nine
396 three hundred (and) ninety six
9,750 nine thousand seven hundred (and) fifty
And можно писать, а можно писать и без and - как учила учительница, так и делайте