The following data types are available in B4R:

Numeric types:

Byte: 0 - 255
Int (2 bytes): -32768 - 32768. Similar to Short type in other B4X tools.
UInt (2 bytes): 0 - 65535.
Long (4 bytes): -2,147,483,648 - 2,147,483,647. Similar to Int type in other B4X tools.
ULong (4 bytes): 0 - 4,294,967,295
Double (4 bytes): 4 bytes floating point. Similar to Float in other B4X tools.
Float is the same as Double. Short is the same as Int.

The above is true on all boards, including the Arduino Due.

Other types:
Boolean: True or False. Practically it is saved as a byte with the value of 1 or 0.
String: Strings are made from an array of bytes that end with a null byte (byte with the value of 0).
Object: Objects can hold other types of values.