4E5

4E5, read as “four times ten to the fifth power,” is a compact representation of the number 400 000 in scientific notation. The format combines a coefficient (typically a decimal between 1 and 10) with an exponent that indicates the power of ten by which the coefficient is multiplied. In the case of 4E5, the coefficient is 4 and the exponent is 5, yielding 4 × 10⁵ = 400 000.

Scientific notation such as 4E5 is widely used across scientific, engineering, and financial fields to express very large or very small quantities succinctly and to reduce the risk of transcription errors. In computer programming and data exchange, the “E” notation is a standardized way to encode floating‑point numbers in plain text, with the letter “E” (or “e”) separating the mantissa from the exponent. Most programming languages, spreadsheets, and data formats (including CSV and JSON) recognize this syntax.

The notation also appears in calculators, measurement instruments, and technical documentation where space is limited. For instance, a sensor that reports a flow rate of 4E5 L h⁻¹ conveys 400 000 litres per hour without requiring additional formatting.

Because the exponent represents a power of ten, numbers expressed as 4E5 can be easily scaled: dividing by 10 gives 4E4 (40 000), while multiplying by 10 yields 4E6 (4 000 000). This linear relationship simplifies unit conversions and logarithmic calculations, making 4E5 a fundamental example of the utility of scientific notation.