Integers are the counting numbers and their negatives . . . . . .
Fact archive: Integer
Math League: integers, whole numbers and their properties (Using Whole Numbers, Place value, Expanded form, Ordering, Rounding whole numbers, Divisibility tests; Operations and their properties: commutative, associative, distributive, zero property, identity, order of operations (PEMDAS))
Construction -- Construction of sets of numbers, starting with the original Peano Axioms, formulated so that zero is included in the set of natural numbers. (See Is Zero a Natural Number?)
The webmaster and author of this Math Help site is Graeme McRae.