NUMBER SENSE · 20 TRIALS
Is the number PRIME or COMPOSITE? Decide before time runs out.
Complete 20 balanced trials. Mistakes and timeouts count, then play continues.
READY?
Press P for PRIME or C for COMPOSITE.
Keyboard: P for prime · C for composite. Touch or mouse: use the two large buttons.
HOW TO PLAY
Start the game and read the integer shown in the center.
Choose PRIME if it has exactly two positive factors. Otherwise choose COMPOSITE.
Complete all 20 standard trials, or protect your endless streak as the timer shrinks.
PRIME NUMBER BASICS
A prime number is a whole number greater than 1 with exactly two positive factors: 1 and itself. For example, 7 is prime because only 1 and 7 divide it evenly.
A composite number has more than two positive factors. For example, 12 is composite because 2, 3, 4, and 6 also divide it. This game uses only 2 through 97, so 0 and 1 never appear.
READ YOUR RESULT
Standard mode always contains 10 prime and 10 composite numbers. Accuracy uses all answers and timeouts; average and best reaction times use correct answers only.
For a fair personal comparison, repeat the same mode on the same device and with the same input method.
QUESTIONS
Yes. Two has exactly two positive factors, 1 and 2. It is also the only even prime number.
No. Every number is from 2 through 97. Zero and one are neither prime nor composite, so they are excluded.
Standard mode records the mistake and continues until all 20 trials are complete. In endless mode, the first mistake or timeout ends the run.
It starts at 2.4 seconds and gets shorter after each correct answer, down to a minimum of half a second.
Yes. Use P and C on a keyboard, or tap the two large on-screen buttons on a phone, tablet, or computer.