2 Lexical conventions [lex]

2.10 Preprocessing numbers [lex.ppnumber]

    . digit
    pp-number digit
    pp-number identifier-nondigit
    pp-number e sign
    pp-number E sign
    pp-number .

Preprocessing number tokens lexically include all integral literal tokens ([lex.icon]) and all floating literal tokens ([lex.fcon]).

A preprocessing number does not have a type or a value; it acquires both after a successful conversion to an integral literal token or a floating literal token.