The number 31221
31221 is a composite number with 6 divisors. Its prime factorisation is × 3469. Divisors (6): 1, 3, 9, 3469, 10407, 31221.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 31221: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 9.
- 2
31221 is composite. Its prime factorisation is
- 3
The divisors add up to 45110; without 31221 itself that is 13889, so 31221 is deficient (13889 is less than 31221). Euler's totient φ(31221) = 20808 numbers up to 31221 share no factor with it.
- 4
The digits of 31221 add up to 9, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 178 steps to reach 1.
LaTeX source of the formulas on this page
\[ 31221 = 3^{2} \times 3469 \]31221 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 6 |
| Sum of divisors | 45110 |
| Euler totient φ(n) | 20808 |
| Square | 974750841 |
| Cube | 30432696006861 |
| Square root | 176.694652 (= 3√3469) |
| Digit sum / digital root | 9 / 9 |
| Collatz steps to 1 | 178 |
| Scientific notation | 3.1221 × |
31221 in other forms
| Form | Value |
|---|---|
| In words | thirty-one thousand two hundred and twenty-one |
| Binary (base 2) | 111100111110101 |
| Octal (base 8) | 74765 |
| Hexadecimal (base 16) | 79F5 |
| Base 3 | 1120211100 |
| As time | 31221 seconds = 8 h 40 min 21 s |
Is 31221 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | No (remainder 1) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (31221 ÷ 3 = 10407) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 1) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 1) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 1) | 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 | No (remainder 5) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (31221 ÷ 9 = 3469) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 1) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 3) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 31221 a prime number?
No. 31221 = × 3469, so it is divisible by 3.
What are the factors of 31221?
1, 3, 9, 3469, 10407, 31221.
What is 31221 in binary?
111100111110101 (hexadecimal 79F5, octal 74765).
What is the square root of 31221?
About 176.6947, exactly 3√3469.
Is 31221 divisible by 3?
Yes. Its digits add up to 9, a multiple of 3.
What is special about the number 31221?
31221 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 9.