Prime and CompositeNumbers with exactly two factors, and everything else.4th GradeA prime number has exactly two factors: 1 and itself.A composite number has more than two.2, 3, 5, 7, 11, 13, 17, 19, 23, 29…7primeOnly 1 × 7. No other pair works.12composite1×12, 2×6, 3×4 — six factors in all.2primeThe only even prime, because every other even number divides by 2.1neitherIt has only one factor, so it fails the 'exactly two' test.THE COMMON MISTAKE✗ 1 is prime✓ 1 is neither prime nor compositePrime means exactly two different factors. 1 has only one.To test a number, try dividing by primes up to its square root. That isenough.Prime and Compositelearnposters.com
Prime and Composite — printable math wall chart from LearnPosters. Free vector PDF, US Letter and A4.

What’s on the Prime and Composite poster

The rule, 4 worked examples, and the mistake everyone makes.

To test a number, try dividing by primes up to its square root. That is enough.

Questions about the Prime and Composite poster

What’s on the Prime and Composite poster?
The rule, 4 worked examples, and the mistake everyone makes. A prime number has exactly two factors: 1 and itself. A composite number has more tha…; 2, 3, 5, 7, 11, 13, 17, 19, 23, 29…; 7 = prime; 12 = composite; 2 = prime; 1 = neither; Common mistake: 1 is prime → 1 is neither prime nor composite. To test a number, try dividing by primes up to its square root. That is enough.
Who is the Prime and Composite poster for?
Prime and Composite is filed under 4th Grade (ages 9–10), so it matches what that year asks a child to remember. It is equally useful to an older student revisiting math, and to the parent or teacher answering the question at the kitchen table.
When should you use the Prime and Composite poster?
Try to arrange counters into a rectangle. Primes only make one long line. A wall chart earns its place by being glanceable from where the work is happening, so Prime and Composite belongs on the wall where that math work actually happens, within glancing distance, rather than filed away.
What other posters go with Prime and Composite?
Adding Fractions, Comparing Decimals and Decimal Place Value sit alongside Prime and Composite in the 4th Grade set. Printed together they make a wall rather than a single sheet, which is how a reference set actually gets used.Adding FractionsComparing DecimalsDecimal Place Value
Is the Prime and Composite poster free to download and print?
Yes. Prime and Composite downloads as a free PDF with no account, no email and no watermark, like everything else in the 4th Grade set. Print as many copies as you like for a home, a classroom, a library or a tutoring group; reselling the file is the only thing the licence rules out.Read the licence
What size does the Prime and Composite poster print at?
Prime and Composite is a vector PDF laid out for US Letter, and prints on A4 with Fit to page — the same file, no separate download. Because every mark on it is drawn rather than photographed, it stays sharp enlarged to A3, A2 or A1 at a copy shop. Colour carries emphasis only, so a greyscale print of Prime and Composite loses nothing.Printing guide

Related posters

Charts that sit alongside Prime and Composite on the same wall.

Browse every 4th Grade poster, or start from the full catalogue.