Free Number Theory Calculators
9 free tools · Prime numbers, factors, GCD, LCM, and other number properties.
9 free number theory calculators
Browse all 300+ calculators →GCD & LCM Calculator — Up to 10 Numbers
Find the GCD and LCM of up to 10 integers using the Euclidean algorithm. Shows prime factorization, divisibility check, and full step-by-step working.
Prime Factorization Calculator
Find the prime factorization of any positive integer and check primality.
Factorial Calculator — n!, n!! & Derangements
Calculate standard factorial (n!), double factorial (n!!), and subfactorial (!n / derangements) with exact BigInt arithmetic, scientific notation, digit count, trailing zeros, Stirling approximation, and step-by-step working.
Fibonacci Calculator — F(n), Sequence & Check
Find any Fibonacci number F(n) with exact BigInt arithmetic up to F(10000), generate sequences with golden ratio convergence, and check whether any integer is a Fibonacci number using the algebraic 5n²±4 perfect-square test.
Prime Number Checker
Check if any number is prime using an optimized trial division algorithm. Also lists factors.
Perfect Number Checker
Check if a number is perfect, abundant, or deficient and find all its proper divisors.
Roman Numeral Converter
Convert between Arabic numbers and Roman numerals (I, V, X, L, C, D, M).
Number Sequence Calculator
Find the nth term of arithmetic, geometric, and other common sequences.
Digital Root Calculator
Calculate the digital root (iterated sum of digits), additive persistence, Harshad check, and multiplicative digital root for any integer up to 300 digits.
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