The number 15720
15720 is a composite number with 32 divisors. Its prime factorisation is × 3 × 5 × 131. Divisors (32): 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120 … 15720.
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How to work it out
- 1
What is special about 15720: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 15.
- 2
15720 is composite. Its prime factorisation is
- 3
The divisors add up to 47520; without 15720 itself that is 31800, so 15720 is abundant (31800 is more than 15720). Euler's totient φ(15720) = 4160 numbers up to 15720 share no factor with it.
- 4
The digits of 15720 add up to 15, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 146 steps to reach 1.
LaTeX source of the formulas on this page
\[ 15720 = 2^{3} \times 3 \times 5 \times 131 \]15720 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 32 |
| Sum of divisors | 47520 |
| Euler totient φ(n) | 4160 |
| Square | 247118400 |
| Cube | 3884701248000 |
| Square root | 125.379424 (= 2√3930) |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 146 |
| Scientific notation | 1.572 × |
15720 in other forms
| Form | Value |
|---|---|
| In words | fifteen thousand seven hundred and twenty |
| Binary (base 2) | 11110101101000 |
| Octal (base 8) | 36550 |
| Hexadecimal (base 16) | 3D68 |
| Base 3 | 210120020 |
| As time | 15720 seconds = 4 h 22 min 0 s |
Is 15720 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (15720 ÷ 2 = 7860) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (15720 ÷ 3 = 5240) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (15720 ÷ 4 = 3930) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (15720 ÷ 5 = 3144) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (15720 ÷ 6 = 2620) | 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 | Yes (15720 ÷ 8 = 1965) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 6) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (15720 ÷ 10 = 1572) | 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 | Yes (15720 ÷ 12 = 1310) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 15720 a prime number?
No. 15720 = × 3 × 5 × 131, so it is divisible by 2.
What are the factors of 15720?
1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120, 131, 262, 393, 524, 655, 786, 1048, 1310, 1572, 1965, 2620, 3144, 3930, 5240, 7860, 15720.
What is 15720 in binary?
11110101101000 (hexadecimal 3D68, octal 36550).
What is the square root of 15720?
About 125.3794, exactly 2√3930.
Is 15720 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 15720?
15720 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 15.