format-number(value, pattern)

Formats value with format defined by pattern. Result is a string:

• 0 : indicates a digit will be placed here
• # : indicates a digit will be placed here if it is not a leading zero
• . : indicates where the decimal point is
• , : indicates where a grouping character will appear

Number	Format	string
0.0123456789	##0	0
-1.234	##0	-1
12345678	##0	12345678
-1.234	000	-001
0.00004	000.000	000.000
0.12345678	000.000	000.012
12345678	000.000	12345678.000
0.00004	##0.0##	0.0
123	##0.0##	123.0
12345678	##0.0##	12345678.0
12345678	###,###,##0.0##	12,345,678.0

Look up the standard or read a book if you need anything more complex!