Oracle - dataype of clob and integer consistent


I have two table

Table name : table1
Column1 : varchar2(10)
Column2 : Number(10)

Table name : table 2
Column1 : clob data look likes ('111','2222','333',............................ very very large data)

Now I create a procedure in oracle(pl/sql)

in procedure ,

update table1 set column1='a' where column2 in (select column1 from table2)

but i have error ORA-00932: inconsistent datatypes: expected - got CLOB in normal query. In table1 cloumn2 is a number but table2 clob datatype so datatype inconsistent error caused. pls suggest me