XSLT Operations

<xsl:when test="ceiling(number($variable1) div number($variable2)) = 2">

You can perform the following operations on XSLT variables:

ceiling($variable): returns the smallest integer greater than or equal to $variable
number($variable): casts $variable to a number
div: performs division operation

string-length()

<xsl :if test="string-length($variable)=0">

You can use the above XSLT IF statement to check whether the length of the $variable is equal to 0.