I would write, one thousand, three hundred and forty as: 1,340
Three hundred thousand: 300,000 Forty three thousand: 43,000 Just in case you were asking for "three hundred forty three thousand": 343,000
Forty two thousand three hundred and one is 42301.
Three thousand, three hundred forty-one.
three hundred forty thousand dollars
you write it: six hundred million forty three thousand three three hundred twenty one.