---
source: ncert
topic: numbers
class_level: class_6
chapter: ch2
difficulty: beginner
---

Class 6 | Ch2: Whole Numbers
Natural Numbers: 1,2,3,... Whole Numbers: 0,1,2,3,... (0 is whole but NOT natural)
Properties: Closure(a+b and a×b always whole), Commutativity(a+b=b+a), Associativity, Distributivity(a×(b+c)=a×b+a×c)
Identity: a+0=a (additive), a×1=a (multiplicative). Zero property: a×0=0.
Predecessor of n=n-1. Successor of n=n+1.
Triangular numbers: 1,3,6,10,15 (n(n+1)/2). Square numbers: 1,4,9,16,25.
Sum 1+2+...+100 = 100×101/2 = 5050.
Common mistake: 0 is NOT natural. Subtraction/division NOT always closed for whole numbers.