Special numbers
Kinds of numbers and sequences
About Special Numbers
Numbers can be classified into many kinds based on their mathematical properties: primes, perfect numbers, Fibonacci numbers, Harshad numbers, and many more. Each kind has a precise definition and appears in number theory, puzzles, or applications.
On NumDic you can look up any number to see which of these kinds it belongs to. Below are the kinds we cover; click one to read a short definition and find links to examples.
Key Features
- Primes, twin primes, and Gaussian primes: divisibility and structure in the integers.
- Fibonacci and perfect numbers: classical sequences and divisor sums.
- Abundant, deficient, Harshad, Kaprekar, Smith, Layland, and palindromic: digit and divisor properties.