All divisors
Last updated 28 August 2026
What the factorisation tells you
Every whole number above one is either prime or a unique product of primes, and that product is more informative than it first looks. The number of divisors falls straight out of it: add one to each exponent and multiply. So 360, which factors as 2³ × 3² × 5, has 4 × 3 × 2 = 24 divisors without anyone needing to list them. Primality testing here uses trial division up to the square root, which is enough for any number this tool accepts — if nothing below the square root divides it, nothing above will either, because factors come in pairs that straddle that point.
Common questions
Why only check divisors up to the square root?
Because factors come in pairs. If a number has a factor larger than its square root, the matching factor must be smaller than the square root — so if nothing small divides it, nothing large will either. That cuts the work enormously.
Is 1 a prime number?
No. A prime has exactly two distinct divisors, one and itself. The number 1 has only one divisor, so it fits neither the definition of prime nor composite — it sits on its own.
How large a number can it handle?
Up to 9,007,199,254,740,991, which is the largest integer JavaScript can represent exactly. Above that, ordinary arithmetic starts losing precision, so the tool declines the input rather than returning a confident wrong answer.
What does the sum of divisors mean?
It adds up every divisor including the number itself. It is how perfect numbers are defined — a number whose divisors excluding itself add up to the number, like 6 (1 + 2 + 3) or 28.