Solitary Number

Solitary Number is a calm, chalkboard-style number puzzle game. Fill in the missing digits and crack the cryptarithms — no clutter, no pressure, just you and the board. TWO CLASSIC PUZZLE WORLDS IN ONE APP • Missing-Digit Arithmetic — restore the hidden digits in +, −, ×, ÷ problems. • Cryptarithms — every letter stands for a digit. Solve famous puzzles like SEND + MORE = MONEY, and the legendary 1923 classic “The Solitary Seven.” FEATURES • 300+ hand-verified puzzles, each with a guaranteed unique solution • Four operations: addition, subtraction, multiplication, division • 2- and 3-term cryptarithms • Historic classic puzzles, with their stories • Handwriting scratchpad — work it out right on the chalkboard • Stats, streaks and an activity heatmap • 4 languages: English, 日本語, ไทย, Tiếng Việt DESIGNED TO FOCUS A deep blackboard, white chalk, and nothing in your way. FREE & PRIVATE • Free to play. Optional one-time “Remove Ads” purchase. • No account, no login, no tracking. Your progress stays on your device. Tap in, fill the blanks, check your answer.