# Solitary Number — Missing-Digit & Cryptarithm

> Missing-Digit & Cryptarithm (iPhone/iPad app by TATSUYA TAGUCHI.)

- Source: https://appshunter.io/ios/app/solitary-number/id6773939414 (this page in markdown: same URL + `.md`)
- Developer: [TATSUYA TAGUCHI](https://appshunter.io/developer/1886335141)
- Category: Education, Games, Board, Puzzle
- Price: Free with in-app purchases
- Age rating: 4+
- Requires: iOS 15.1 · 40 MB
- Languages: American English
- Released: 2026-06-02
- Data updated: 2026-09-09
- User reviews in markdown: https://appshunter.io/ios/app/solitary-number/id6773939414/reviews.md

## What is 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.

## Pricing and in-app purchases

Base price: Free.

**One-time purchases**

| Purchase | Price | Type |
| --- | --- | --- |
| Remove Ads | $2.99 | one-time |



## Version history (last 1 release)

### 1.0 — 2026-06-02

No release notes.

## More apps by TATSUYA TAGUCHI

- [おかいものノート](https://appshunter.io/ios/app/id6760806523)
- [Sensei Japanese](https://appshunter.io/ios/app/sensei-japanese/id6761647436)
- [BookMarch](https://appshunter.io/ios/app/bookmarch/id6761997830)
- [Small Tap: Habit Tracker](https://appshunter.io/ios/app/small-tap-habit-tracker/id6765972749)
- [Pawendar](https://appshunter.io/ios/app/pawendar/id6768890849)
- [MalaLog](https://appshunter.io/ios/app/malalog/id6771284016)

All apps by TATSUYA TAGUCHI: https://appshunter.io/developer/1886335141

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-09.*