double value = 1427799000;
Console.WriteLine(value.ToString("G2", CultureInfo.InvariantCulture));
//output: 1.4E+09
The General ("G") Format Specifier
The general ("G") format specifier converts a number to the most
compact of either fixed-point or scientific notation, depending on the
type of the number and whether a precision specifier is present.
EDIT: About your comment you can't display the scientific notation in your desirable way, it is not defined that way ! The coeficient must be greater or equal to 1 and less to 10.
For number 1.23*10^11 ->Article source
The first number 1.23 is called the coefficient. It must be greater than or equal to 1 and less than 10.
The second number is called the base . It must always be 10 in
scientific notation. The base number 10 is always written in exponent
form. In the number 1.23 x 10^11 the number 11 is referred to as the
exponent or power of ten.