# tonumber(e [, base])

Tries to convert its argument to a number. If the argument is already a number or a
string convertible to a number, then `tonumber`

returns this number; otherwise, it
returns **null**.

An optional argument specifies the base to interpret the numeral. The base may be any integer
between 2 and 36, inclusive. In bases above 10, the letter '`A`

' (in either upper or
lower case) represents 10, '`B`

' represents 11, and so forth, with
'`Z`

' representing 35. In base 10 (the default), the number can have a decimal part,
as well as an optional exponent part (see Values and
Types). In other bases, only unsigned integers are accepted.