How do I convert this value 1.2851048260000018E7 (double) to int datatype in a SQL query?

I'm assuming you're not really looking for int, but rather a non-scientific notation. If you simply want dollars and cents use the following (since you didn't provide sample code/data, you'll have to adjust this for your query):

SELECT CAST(1.2851048260000018E7 AS decimal(18,2))

If you need more decimal digits for calculations, use whatever would be appropriate for scale with the syntax decimal(precision, scale), described here.

If you really are looking for an int datatype, that is dollars with cents rounded, use:

SELECT CAST(ROUND(1.2851048260000018E7, 0) AS int)

Use caution if leaving out the ROUND function. When you CAST a decimal to int, the number will be truncated at the decimal point, not rounded.