The number 31521
31521 is a composite number with 16 divisors. Its prime factorisation is 3 × 7 × 19 × 79. Divisors (16): 1, 3, 7, 19, 21, 57, 79, 133, 237, 399, 553, 1501, 1659, 4503, 10507, 31521.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
31521 has no famous special property in the usual lists (prime, square, cube, triangular, Fibonacci, palindrome, perfect), but it is still a composite number.
- 2
31521 is composite. Its prime factorisation is
- 3
The divisors add up to 51200; without 31521 itself that is 19679, so 31521 is deficient (19679 is less than 31521). Euler's totient φ(31521) = 16848 numbers up to 31521 share no factor with it.
- 4
The digits of 31521 add up to 12, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 178 steps to reach 1.
LaTeX source of the formulas on this page
\[ 31521 = 3 \times 7 \times 19 \times 79 \]
31521 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 51200 |
| Euler totient φ(n) | 16848 |
| Square | 993573441 |
| Cube | 31318428433761 |
| Square root | 177.541544 |
| Digit sum / digital root | 12 / 3 |
| Collatz steps to 1 | 178 |
| Scientific notation | 3.1521 × |
31521 in other forms
| Form | Value |
|---|---|
| In words | thirty-one thousand five hundred and twenty-one |
| Binary (base 2) | 111101100100001 |
| Octal (base 8) | 75441 |
| Hexadecimal (base 16) | 7B21 |
| Base 3 | 1121020110 |
| As time | 31521 seconds = 8 h 45 min 21 s |
Is 31521 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 (31521 ÷ 3 = 10507) | 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 | Yes (31521 ÷ 7 = 4503) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 3) | 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 6) | 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 31521 a prime number?
No. 31521 = 3 × 7 × 19 × 79, so it is divisible by 3.
What are the factors of 31521?
1, 3, 7, 19, 21, 57, 79, 133, 237, 399, 553, 1501, 1659, 4503, 10507, 31521.
What is 31521 in binary?
111101100100001 (hexadecimal 7B21, octal 75441).
What is the square root of 31521?
About 177.5415.
Is 31521 divisible by 3?
Yes. Its digits add up to 12, a multiple of 3.
What is special about the number 31521?
It is a composite number with 16 divisors.