Prime Time

How to play

A prime has exactly two positive divisors. Classify the number.

Controls

Tap the board · Tab + Enter · Answer keys 1–4 where shown

A few ways to improve

• Eliminate simple composites first. Every even number greater than two is composite; numbers ending in five or zero are composite unless the number is five itself. A digit sum divisible by three also reveals divisibility by three.
• For a candidate that survives those checks, test divisors only up to its square root. If no integer divisor exists by then, a larger complementary divisor cannot appear on its own.

Difficulty and daily progress

A round lasts 30 seconds. Every three starts of Prime Time raise its daily difficulty, up to difficulty 10. Your count resets at 00:00 UTC, so tomorrow begins with the starting challenge again. The clock continues if you switch tabs, and leaving ends the attempt.

Scores and rewards

The score measures this game’s performance. Reward points are a separate account balance. Practice rounds earn no points or XP and do not enter the rewarded leaderboard. Rewarded rounds require sign-in, human verification, active play, and live gameplay checks before a result is saved. Idle or abandoned rounds do not earn rewards.

After an eligible rewarded round, keep its sponsored claim page focused for 12 seconds and complete a fresh hCaptcha. Then select Claim reward to add the pending points and XP to your account. No advertisement click or purchase is needed. You can return to an unfinished claim from the arcade; another rewarded round becomes available after that claim is collected or skipped.

Account points currently unlock site cosmetics. Each player level after level 1 adds a 0.1% bonus to points earned from games. Read the fair-play rules or visit Support if a round needs help.