That is simply 640 million;
it is written as 640,000,000 in the English-speaking world
and as 640.000.000 elsewhere.
23,064,907
64 000 000
six thousand four hundred 6,400
64,086,300
7,064,001,213.032
64 000 000
23,064,907
64 000 000
64 400 000
six thousand four hundred 6,400
9,064,052
64,086,300
7,064,001,213.032
Thusly: 25,718,000,001,064
26 and 56 that is, 64 and 15625
Five hundred twelve one-thousandths is 512/1,000, which reduces to 64/125 or 0.512.
6.4 million in standard form is 6.4 × 106(standard notation is 6,400,000)