Divisors of 399: All 8 Factors

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 399

The number 399 has 8 divisors:

1,  3,  7,  19,  21,  57,  133,  399

Divisor Pairs of 399

Each pair multiplies to 399:

Number of Divisors

The number 399 has 8 divisors, written as τ(399) = 8 in number theory.

Sum of Divisors

σ(399) = 1 + 3 + 7 + 19 + 21 + 57 + 133 + 399 = 640

Prime Factorization of 399

See the full prime factorization calculator →

Properties of 399

• 399 is composite.
• 399 is not a perfect square.
• Number of divisors: 8.
• Sum of divisors: 640.

Common Divisors with Another Number?

Looking for the divisors that 399 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 399

An efficient way to find divisors uses the complementary pair trick: check each integer i from 1 to √399 ≈ 19.97. If i divides 399, then both i and 399/i are divisors.

1. 1 divides 399 (399 ÷ 1 = 399) → pair (1, 399)
2. 3 divides 399 (399 ÷ 3 = 133) → pair (3, 133)
3. 7 divides 399 (399 ÷ 7 = 57) → pair (7, 57)
4. 19 divides 399 (399 ÷ 19 = 21) → pair (19, 21)
5. Collect all unique values: {1, 3, 7, 19, 21, 57, 133, 399} — total 8 divisors.
6. Sum: 1 + 3 + 7 + 19 + 21 + 57 + 133 + 399 = 640.

Nearby Examples

Related Operations for 399

• Multiples of 399 — "outward" complement; M is a multiple of 399 ⇔ 399 is a divisor of M
• 399 Prime Factorization — decompose into prime building blocks
• Find GCF of 399 and another number
• Find LCM of 399 and another number
• Is 399 a perfect square? (odd divisor count ⇔ yes)

See also our tables of divisors:

• Table of all divisors from 1 to 100
• Table of all divisors from 1 to 500
• Table of all divisors from 1 to 1,000
• Table of all divisors from 1 to 10,000

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.

References

• [1] Divisor (Wikipedia)
• [2] Divisor function (Wikipedia)
• [3] Divisor (Wolfram MathWorld)

Divisors Calculation Examples

Find all divisors of these numbers: