SUUGAKU
Kaprekar Numbers
Sort digits, subtract, repeat. Every number converges to 495 or 6174.
Enjoy Numbers
Numbers are stranger than you think.
Enter any number and watch it transform. 14 interactive themes turn famous mathematical wonders into something you can touch.
14 themes to explore
Collatz Sequence
An unsolved conjecture you can trace on a graph.
Perfect & Amicable
Numbers whose divisors add up to themselves, or to each other.
Prime Numbers
Checks, factorization, the sieve, twin primes and Mersenne primes.
Fibonacci Sequence
Compute, check and graph the sequence found in nature.
Harshad Numbers
Numbers divisible by the sum of their digits.
Magic Squares
Rows, columns and diagonals with equal sums, built in animation.
Goldbach's Conjecture
Split even numbers into two primes and count the pairs.
Smith Numbers
Composites whose digit sum matches that of their prime factors.
Happy Numbers
Square the digits, add, repeat. Will you reach 1?
Palindrome Numbers
Same both ways, plus the reverse-and-add puzzle of 196.
Pythagorean Triples
a² + b² = c² and its right triangles.
Triangular Numbers
Arrange dots into a triangle and see n(n+1)/2.
Narcissistic Numbers
153 = 1³ + 5³ + 3³, and others like it.
Made for curiosity
See every step
Animations and graphs show how each result comes about.
Private by design
All calculations run on your device. No account needed.
Your language
Available in many languages, with dark and light themes.
Start playing with numbers
iOS 17.0 or later / Android 8.0 or later. The app shows ads.