Number Theory
Basic

Divisibility Rule for 3

A number is divisible by 3 if the sum of its digits is.

Formula

n divisible by 3  ⟺  digit sum divisible by 3n \text{ divisible by } 3 \iff \text{digit sum divisible by } 3

Variables

nInteger

Example

123: 1+2+3=6 ✓

Did You Know?

A number is divisible by 3 exactly when its digits sum to a multiple of 3 — try it on 12,345.

divisibilityrulebasic