Add name space to the style sheet:

<xsl:stylesheet
  version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:uti="http://soap.postserver.aedsicad.com/uti.xsd"
  xmlns:java="http://xml.apache.org/xalan/java"
  xmlns:xalan="http://xml.apache.org/xalan"
  xmlns:utiapi="xalan://com.aedsicad.postserver.api.XSLHelper"
  xmlns:stringutils="org.apache.commons.lang3.StringUtils"
  xmlns:mathutils="org.apache.commons.math3.util.Precision"
  xmlns:sap="urn:x4/SAP_GIS_Connector"
  exclude-result-prefixes="java xalan uti utiapi stringutils mathutils">  

Example of a number rounded to 2 digits:
<xsl:value-of select="stringutils:replace(mathutil:round(number($UTM_COORD[1]),2),'.',',')" />

Check out more on the Apache Commons Math (Apache License, Version 2.0) Apache Commons Math (org.apache.commons:commons-math3:3.6.1 ).