The number 31813
31813 is a palindrome: it reads 31813 backwards too. Its prime factorisation is 29 × 1097. Divisors (4): 1, 29, 1097, 31813.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 31813: a palindrome: it reads 31813 backwards too; a semiprime: 29 × 1097, the product of two primes.
- 2
31813 is composite. Its prime factorisation is
- 3
The divisors add up to 32940; without 31813 itself that is 1127, so 31813 is deficient (1127 is less than 31813). Euler's totient φ(31813) = 30688 numbers up to 31813 share no factor with it.
- 4
The digits of 31813 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 98 steps to reach 1.
LaTeX source of the formulas on this page
\[ 31813 = 29 \times 1097 \]
31813 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 32940 |
| Euler totient φ(n) | 30688 |
| Square | 1012066969 |
| Cube | 32196886484797 |
| Square root | 178.361991 |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 98 |
| Scientific notation | 3.1813 × |
31813 in other forms
| Form | Value |
|---|---|
| In words | thirty-one thousand eight hundred and thirteen |
| Binary (base 2) | 111110001000101 |
| Octal (base 8) | 76105 |
| Hexadecimal (base 16) | 7C45 |
| Base 3 | 1121122021 |
| As time | 31813 seconds = 8 h 50 min 13 s |
Is 31813 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 | No (remainder 1) | 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 3) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 1) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 5) | 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 | No (remainder 7) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 3) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 1) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 31813 a prime number?
No. 31813 = 29 × 1097, so it is divisible by 29.
What are the factors of 31813?
1, 29, 1097, 31813.
What is 31813 in binary?
111110001000101 (hexadecimal 7C45, octal 76105).
What is the square root of 31813?
About 178.3620.
Is 31813 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 31813?
31813 is a palindrome: it reads 31813 backwards too; a semiprime: 29 × 1097, the product of two primes.