Datatype Limits

Datatypes	Limit	Comments
BFILE	Maximum size: 4 GB Maximum size of a file name: 255 characters Maximum size of a directory name: 30 characters Maximum number of open BFILEs: see Comments	The maximum number of BFILEs is limited by the value of theSESSION_MAX_OPEN_FILES initialization parameter, which is itself limited by the maximum number of open files the operating system will allow.
BLOB	Maximum size: (4 GB - 1) * DB_BLOCK_SIZEinitialization parameter (8 TB to 128 TB)	The number of LOB columns per table is limited only by the maximum number of columns per table (that is, 1000Foot 1 ).
CHAR	Maximum size: 2000 bytes	None
CHAR VARYING	Maximum size: 4000 bytes	None
CLOB	Maximum size: (4 GB - 1) * DB_BLOCK_SIZEinitialization parameter (8 TB to 128 TB)	The number of LOB columns per table is limited only by the maximum number of columns per table (that is, 1000Footref 1).
Literals (characters or numbers in SQL or PL/SQL)	Maximum size: 4000 characters	None
LONG	Maximum size: 2 GB - 1	Only one LONG column is allowed per table.
NCHAR	Maximum size: 2000 bytes	None
NCHAR VARYING	Maximum size: 4000 bytes	None
NCLOB	Maximum size: (4 GB - 1) * DB_BLOCK_SIZEinitialization parameter (8 TB to 128 TB)	The number of LOB columns per table is limited only by the maximum number of columns per table (that is, 1000Footref 1).
NUMBER	999...(38 9's) x10125 maximum value -999...(38 9's) x10125 minimum value	Can be represented to full 38-digit precision (the mantissa) Can be represented to full 38-digit precision (the mantissa)
Precision	38 significant digits	None
RAW	Maximum size: 2000 bytes	None
VARCHAR	Maximum size: 4000 bytes	None
VARCHAR2	Maximum size: 4000 bytes	None

Footnote 1 The absolute maximum number of columns in a table is 1000. However, when you create an object table (or a relational table with columns of object, nested table, varray, or REF type), Oracle maps the columns of the user-defined types to relational columns, creating in effect hidden columns that count toward the 1000-column limit. For details on how Oracle calculates the total number of columns in such a table, refer to Oracle Database Administrator's Guide.

for reference - 

https://docs.oracle.com/cd/B28359_01/server.111/b28320/limits001.htm