SQLPLUS formatting output in excel

Below is the code to retrieve data from DB and output it in excel

sqlplus -s ${uidpwd} <<EOF
SET PAGESIZE 50000
SET FEEDBACK OFF
SET MARKUP HTML ON
SET NUM 24
SPOOL Extract.xls

whenever oserror exit 9
whenever sqlerror exit sql.sqlcode  
@${SQL_SCRIPT}
SET SERVEROUTPUT ON
SET ECHO OFF
SET VERIFY OFF
SPOOL OFF
SET MARKUP HTML OFF
quit;
EOF

But what i see in excel report is all numbers in excel are with exponential like "5.30056E+15" i tried below options, but none of them worked

SET NUMBERFORMAT '9999999999999999999999'

SET NUMWIDTH 20

in SQL i tried below

to_char(conf_num, '999999999999999999999999')

SELECT ' '||conf_num "Confirmation Number"

Also i have exec > ${LOGPATH}/log.``date +"%y%m%d"``.log 2>&1 in my script, Query out put is getting written in to this log file, how to avoid that? It should have only error logs.