Possible rounding error of large float values?

When setting a float column to this value:

9223372036854775807

It gets selected out as:

9.22337203685478E18

Which appears to be rounded. When we cast it to numeric type we get:

9223372036854780000

Which also is rounded. It is still possible to find the row using the
original value

select * from <table> where <col> = 9223372036854775807

Is this expected behavior?

Thanks,
Adam