Divisors of 405: All 10 Factors
Quick Answer
405 has 10 divisors (factors): 1, 3, 5, 9, 15, 27, 45, 81, 135, 405.
Sum: 726.
Divisors (Factors) Calculator
Use the calculator above to find all divisors (also called factors) of any positive integer up to 4,782,969. Beyond the divisor list, this tool also shows divisor pairs, the sum and count of divisors, prime factorization, and number properties (prime, perfect square, perfect number).
All Divisors of 405
The number 405 has 10 divisors:
1, 3, 5, 9, 15, 27, 45, 81, 135, 405
Divisor Pairs of 405
Each pair multiplies to 405:
| Factor 1 | × | Factor 2 | = | Product |
|---|---|---|---|---|
| 1 | × | 405 | = | 405 |
| 3 | × | 135 | = | 405 |
| 5 | × | 81 | = | 405 |
| 9 | × | 45 | = | 405 |
| 15 | × | 27 | = | 405 |
Number of Divisors
The number 405 has 10 divisors, written as τ(405) = 10 in number theory.
Sum of Divisors
σ(405) = 1 + 3 + 5 + 9 + 15 + 27 + 45 + 81 + 135 + 405 = 726
Prime Factorization of 405
Properties of 405
- 405 is composite.
- 405 is not a perfect square.
- Number of divisors: 10.
- Sum of divisors: 726.
Common Divisors with Another Number?
Looking for the divisors that 405 shares with another number? Use our Greatest Common Factor (GCF) calculator — it finds all common divisors and the largest one.
Step-by-Step: How to Find the Divisors of 405
An efficient way to find divisors uses the complementary pair trick: check each integer i from 1 to √405 ≈ 20.12. If i divides 405, then both i and 405/i are divisors.
- 1 divides 405 (405 ÷ 1 = 405) → pair (1, 405)
- 3 divides 405 (405 ÷ 3 = 135) → pair (3, 135)
- 5 divides 405 (405 ÷ 5 = 81) → pair (5, 81)
- 9 divides 405 (405 ÷ 9 = 45) → pair (9, 45)
- 15 divides 405 (405 ÷ 15 = 27) → pair (15, 27)
- Collect all unique values: {1, 3, 5, 9, 15, 27, 45, 81, 135, 405} — total 10 divisors.
- Sum: 1 + 3 + 5 + 9 + 15 + 27 + 45 + 81 + 135 + 405 = 726.
Nearby Examples
Related Operations for 405
- Multiples of 405 — "outward" complement; M is a multiple of 405 ⇔ 405 is a divisor of M
- 405 Prime Factorization — decompose into prime building blocks
- Find GCF of 405 and another number
- Find LCM of 405 and another number
- Is 405 a perfect square? (odd divisor count ⇔ yes)
See also our tables of divisors:
What Is a Divisor?
A divisor (also called a factor) of a positive integer n is any positive integer d such that n ÷ d has no remainder. In other words, d divides n evenly.
Every positive integer n has at least two divisors: 1 and n itself (with 1 being the trivial case of having only itself). Numbers with exactly 2 divisors are prime; numbers with 3 or more divisors are composite.
Why use this calculator? Beyond just listing divisors, this tool computes the sum σ(n), the count τ(n), prime factorization, divisor pairs (useful for visual learners and factoring problems), and detects whether n is a prime, a perfect square, or a perfect number.
Divisors Calculation Examples
Find all divisors of these numbers:
Related Calculators
- Multiples of a Number — "outward" complement
- Prime Factorization — product of prime divisors
- Greatest Common Factor (GCF) — largest common divisor of 2+ numbers
- Least Common Multiple (LCM) — smallest common multiple
- Is N a Perfect Square? — odd divisor count check