The output will be the number 123. The Number() function is used for explicit type conversion in JavaScript. When a string containing only numeric characters is passed to Number(), it converts the string to its numeric equivalent. This is different from implicit coercion that happens in operations like '123' - 0, which would also result in 123. The Number() function can also convert other data types: Number(true) gives 1, Number(false) gives 0, and Number(null) gives 0, while Number(undefined) and Number('abc') result in NaN.