Category
Culture & curiosities
Numerals across writing systems, lucky numbers, number trivia and mathematical oddities.
12 generators
Angel numbers
What the New Age literature says 111, 444, 1111 and the other repeating sequences mean — attributed, dated and with no claim that any of it works.
Benford law distribution
Expected first- and second-digit frequencies under Benford’s law, plus a reproducible dataset that follows it exactly.
Digital roots
Add a number’s digits until one digit is left. The medieval arithmetic check behind casting out nines, in any base from 2 to 36.
A010888Facts about any number
Enter a number and get everything provable about it — primality, factors, divisors, bases, Roman numerals — plus the real story behind the famous ones.
Lucky and unlucky numbers
Which numbers are treated as lucky or unlucky in China, Japan, Korea, Italy, Turkey, India and the West — and the entirely unrelated lucky numbers of Ulam's sieve.
A000959Named large numbers
Million, billion, googol and beyond — including why a billion means two different things depending on where you are.
Numerals in other writing systems
Write the same number in Devanagari, Arabic-Indic, Chinese, Japanese, Roman, Greek, Hebrew, Thai, tally marks or Babylonian cuneiform.
Numerology numbers
Life path, expression and soul urge numbers worked out from a birth date and a name, with both the Pythagorean and Chaldean charts — presented as cultural history, not prediction.
Palindrome dates
Which days read the same backwards — worked out separately for DD/MM/YYYY, MM/DD/YYYY and YYYY-MM-DD, because palindromy is a property of notation rather than of time.
Palindromic numbers
Numbers that read the same in both directions — in base 10 or any base up to 36, optionally narrowed to primes, squares or cubes.
A002113Prime factorisation
Split any whole number into its prime factors with exponents, using a 30-wheel trial division that works on big integers.
A027746Ulam spiral coordinates
Winds the integers outward from a centre cell and marks the primes, drawing out the diagonal lines Stanisław Ulam spotted on graph paper in 1963.