The number 15820
15820 is a composite number with 24 divisors. Its prime factorisation is × 5 × 7 × 113. Divisors (24): 1, 2, 4, 5, 7, 10, 14, 20, 28, 35, 70, 113, 140, 226, 452, 565 … 15820.
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How to work it out
- 1
What is special about 15820: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
15820 is composite. Its prime factorisation is
- 3
The divisors add up to 38304; without 15820 itself that is 22484, so 15820 is abundant (22484 is more than 15820). Euler's totient φ(15820) = 5376 numbers up to 15820 share no factor with it.
- 4
The digits of 15820 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 146 steps to reach 1.
LaTeX source of the formulas on this page
\[ 15820 = 2^{2} \times 5 \times 7 \times 113 \]15820 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 24 |
| Sum of divisors | 38304 |
| Euler totient φ(n) | 5376 |
| Square | 250272400 |
| Cube | 3959309368000 |
| Square root | 125.777581 (= 2√3955) |
| Digit sum / digital root | 16 / 7 |
| Collatz steps to 1 | 146 |
| Scientific notation | 1.582 × |
15820 in other forms
| Form | Value |
|---|---|
| In words | fifteen thousand eight hundred and twenty |
| Binary (base 2) | 11110111001100 |
| Octal (base 8) | 36714 |
| Hexadecimal (base 16) | 3DCC |
| Base 3 | 210200221 |
| As time | 15820 seconds = 4 h 23 min 40 s |
Is 15820 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (15820 ÷ 2 = 7910) | 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 (15820 ÷ 4 = 3955) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (15820 ÷ 5 = 3164) | 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 | Yes (15820 ÷ 7 = 2260) | 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 4) | 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 (15820 ÷ 10 = 1582) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 2) | 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 15820 a prime number?
No. 15820 = × 5 × 7 × 113, so it is divisible by 2.
What are the factors of 15820?
1, 2, 4, 5, 7, 10, 14, 20, 28, 35, 70, 113, 140, 226, 452, 565, 791, 1130, 1582, 2260, 3164, 3955, 7910, 15820.
What is 15820 in binary?
11110111001100 (hexadecimal 3DCC, octal 36714).
What is the square root of 15820?
About 125.7776, exactly 2√3955.
Is 15820 divisible by 3?
No. Its digits add up to 16, which is not a multiple of 3.
What is special about the number 15820?
15820 is a happy number: repeatedly adding the squares of its digits reaches 1.