The number 15813
15813 is a composite number with 12 divisors. Its prime factorisation is × 7 × 251. Divisors (12): 1, 3, 7, 9, 21, 63, 251, 753, 1757, 2259, 5271, 15813.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 15813: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
15813 is composite. Its prime factorisation is
- 3
The divisors add up to 26208; without 15813 itself that is 10395, so 15813 is deficient (10395 is less than 15813). Euler's totient φ(15813) = 9000 numbers up to 15813 share no factor with it.
- 4
The digits of 15813 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 53 steps to reach 1.
LaTeX source of the formulas on this page
\[ 15813 = 3^{2} \times 7 \times 251 \]15813 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 12 |
| Sum of divisors | 26208 |
| Euler totient φ(n) | 9000 |
| Square | 250050969 |
| Cube | 3954055972797 |
| Square root | 125.749751 (= 3√1757) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 53 |
| Scientific notation | 1.5813 × |
15813 in other forms
| Form | Value |
|---|---|
| In words | fifteen thousand eight hundred and thirteen |
| Binary (base 2) | 11110111000101 |
| Octal (base 8) | 36705 |
| Hexadecimal (base 16) | 3DC5 |
| Base 3 | 210200200 |
| As time | 15813 seconds = 4 h 23 min 33 s |
Is 15813 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 (15813 ÷ 3 = 5271) | 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 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (15813 ÷ 7 = 2259) | 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 (15813 ÷ 9 = 1757) | 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 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 15813 a prime number?
No. 15813 = × 7 × 251, so it is divisible by 3.
What are the factors of 15813?
1, 3, 7, 9, 21, 63, 251, 753, 1757, 2259, 5271, 15813.
What is 15813 in binary?
11110111000101 (hexadecimal 3DC5, octal 36705).
What is the square root of 15813?
About 125.7498, exactly 3√1757.
Is 15813 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 15813?
15813 is a happy number: repeatedly adding the squares of its digits reaches 1.