Solitary Number
Missing-Digit & Cryptarithm
Free · In‑App Purchases · Designed for iPad. Not verified for macOS.
100% free, no tracking. Fill in the missing digits and crack cryptarithms on a calm chalkboard — including the legendary 1923 classic, The Solitary Seven.
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.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
The developer, TATSUYA TAGUCHI, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Linked to You
The following data may be collected but it is not linked to your identity:
- Purchases
- Location
- Identifiers
- Usage Data
- Diagnostics
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- TATSUYA TAGUCHI
- Size
- 42.3 MB
- Category
- Education
- Compatibility
Requires iOS 15.1 or later.
- iPhone
Requires iOS 15.1 or later. - iPad
Requires iPadOS 15.1 or later. - iPod touch
Requires iOS 15.1 or later. - Mac
Requires macOS 12.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
- English
- Age Rating
4+
- 4+
- Contains
Advertising
- In-App Purchases
Yes
- Remove Ads $2.99
- Copyright
- © 2026 TaTsuya