What is a least count of digital micrometer?

A micrometer is automaticly metric.

A micrometre, American spelling: micrometer; symbol µm, is one millionth of a metre, or equivalently one thousandth of a millimetre. It is also commonly known as a micron. It can be written in scientific notation as 1×10−6 m, meaning 1/1 000 000 m.