Welcome to this addition of the PowerShell ABC's where you'll find 26 posts detailing a component of the PowerShell scripting language, one letter at a time. Today's letter is the letter "N" and for this letter I'm going to discuss one of the core types of objects you'll likely be dealing with: Numbers.
PowerShell supports all of the basic .NET numeric types and performs conversions to and from the different types as needed. The types, along with the PowerShell type names are in the following table

.NET Full Type Name   PowerShell Short Type Name   Example 

System.Int32  [int]  1 
System.Int64  [long]  4294967296 
System.Double  [double]  1.2 
System.Decimal  [decimal]  1d 

Default Type Determiniation
If you don't specify a type for a literal, the system will figure out the best type and way to represent the number.
Integers (System.Int32) will be used by default and if the literal value is too large to fit into a 32bit integer, then a long 64bit integer (System.Int64) will be used. If it's too large for a 64 bit integer, or if it contains a decimal point, then a double (System.Double) will be used.
The System.Single type is supported but is typically not used as it provides no advantages over the System.Double type.
There is one condition where you will want to specify the type and that would be for the decimal type (System.Decimal). This is done by placing a "d" after the number with no whitespace in between.
Multiplier Suffixes
The PowerShell team was kind enough to add some special suffixes for numbers to make managing larger numbers easier. The following table lists the special powers of two modifiers supported by PowerShell

Multiplier Suffix   Multiplication Factor   Example   Equivalent Value   .NET Type 

kb  1024  1kb  1024  System.Int32 
  1.1kb  1126.4  System.Double 
mb  1024*1024  1mb  1048576  System.Int32 
  1.1mb  1153433.6  System.Double 
gb  1024*1024*1024  1gb  1073741824  System.Int32 
  1.1gb  1181116006.4  System.Double 
tb*  1024*1024*1024*1024  1tb  1099511627776  System.Int64 
  1.1tb  1209462790553.6  System.Double 
pb*  1024*1024*1024*1024*1024  1pb  1125899906842624  System.Int64 
  1.1pb  1.23848989752689E+15  System.Double 

*Note, that tb (terabyte) and pb (petabyte) were added in PowerShell v2.
Don't forget the hexidecimals
The last type of number literals are hexidecimals. Hexidecimal numbers are in base16 and thus use the 16 distinct symbols [09] and [AF] to represent the values 015 respectively. PowerShell follows the same notation as C, C++, C#, and many other languages in that you prefix the number with the sequence ZeroX ("0x") and allowing the letters AF (in either case) as extra digits. 0x10 > 16, 0xF > 16, and so on.