Skip to content

MathCastle.org Courses

0 XPLogin Sign up

Progress dashboard Review missed Leaderboards Search

Grade 4 Grade 5 Grade 6 Pre-Algebra Algebra 1 Algebra 2 Geometry Trigonometry Precalculus Calculus Multivariable Calculus Linear Algebra Differential Equations Counting & Probability Statistics & Data Number Theory Groups and Fields Graph Theory Proof Writing

Pre-AlgebraEasyDivisibility

Divisibility · Easy problem

Is $21$ prime or composite?

Practice more like this Review this concept

MathCastle.org · every problem original, every answer machine-checked. ∎

About Search Leaderboards Privacy Terms