RE: displaying characters

This is probably a simple question but i have looked around.

Im trying to use the below characters in my output of my transform
	
Dec	Octal	Name	Value
	1	001	SOH	^A
	2	002	STX	^B
	3	003	ETX	^C
	4	004	EOT	^D
	5	005	ENQ	^E
	21	025	NAK	^U
	28	034	FS	^\
	30	036	RS	^^
	127	177	DEL	^?

Using the normal way of 

<xsl:text>&#21;</xsl:text>

Brings up the below error...

example.xsl:87: parser error : xmlParseCharRef: invalid xmlChar value 21
<xsl:text>&#21;</xsl:text>

Now for standard characters this works but not for these.

Any helo would be appreciated.

Cheers