It is no wonder you are having trouble writing it (them?). The way the question is stated, this is not one single number, but two at least. 9 hundred is 900. And since one thousand millions is one billion in US notation, 1250 million would be the same as one billion two hundred fifty million, 1,250,000,000. The language of the question is too confused to make one number out of it. Do you mean 900 billion, 900 million, 900 thousand, or just plain 900?
900,000,000
Well, write it out, a hundred million is 100,000,000. That is 9 digits, if that's what you mean.
9,200,000,000
1,925,000 or 1.925 million.
49,000,999
5,065,900
Nine million, one hundred twenty thousand, seven hundred forty
Nine million five hundred thousand - or - Nine and a half million.
9,186,000
nine million two hundred seventy-four thousand five hundred seventy-three
9 700 045 306
9, 212 , 345 nine million, two hundred twelve thousand, three hundred forty five.