The number 31840
31840 is a composite number with 24 divisors. Its prime factorisation is × 5 × 199. Divisors (24): 1, 2, 4, 5, 8, 10, 16, 20, 32, 40, 80, 160, 199, 398, 796, 995 … 31840.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 31840: a Harshad number: divisible by its digit sum 16.
- 2
31840 is composite. Its prime factorisation is
- 3
The divisors add up to 75600; without 31840 itself that is 43760, so 31840 is abundant (43760 is more than 31840). Euler's totient φ(31840) = 12672 numbers up to 31840 share no factor with it.
- 4
The digits of 31840 add up to 16, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 28 steps to reach 1.
LaTeX source of the formulas on this page
\[ 31840 = 2^{5} \times 5 \times 199 \]31840 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 75600 |
| Euler totient φ(n) | 12672 |
| Square | 1013785600 |
| Cube | 32278933504000 |
| Square root | 178.437664 (= 4√1990) |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 28 |
| Scientific notation | 3.184 × |
31840 in other forms
| Form | Value |
|---|---|
| In words | thirty-one thousand eight hundred and forty |
| Binary (base 2) | 111110001100000 |
| Octal (base 8) | 76140 |
| Hexadecimal (base 16) | 7C60 |
| Base 3 | 1121200021 |
| As time | 31840 seconds = 8 h 50 min 40 s |
Is 31840 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (31840 ÷ 2 = 15920) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | No (remainder 1) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (31840 ÷ 4 = 7960) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (31840 ÷ 5 = 6368) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 4) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 4) | A number is divisible by 7 if double the last digit and subtract it from the rest: the result is a multiple of 7. |
| 8 | Yes (31840 ÷ 8 = 3980) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 7) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (31840 ÷ 10 = 3184) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 6) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 4) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 31840 a prime number?
No. 31840 = × 5 × 199, so it is divisible by 2.
What are the factors of 31840?
1, 2, 4, 5, 8, 10, 16, 20, 32, 40, 80, 160, 199, 398, 796, 995, 1592, 1990, 3184, 3980, 6368, 7960, 15920, 31840.
What is 31840 in binary?
111110001100000 (hexadecimal 7C60, octal 76140).
What is the square root of 31840?
About 178.4377, exactly 4√1990.
Is 31840 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 31840?
31840 is a Harshad number: divisible by its digit sum 16.