The number 31128
31128 is a composite number with 16 divisors. Its prime factorisation is × 3 × 1297. Divisors (16): 1, 2, 3, 4, 6, 8, 12, 24, 1297, 2594, 3891, 5188, 7782, 10376, 15564, 31128.
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How to work it out
- 1
What is special about 31128: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
31128 is composite. Its prime factorisation is
- 3
The divisors add up to 77880; without 31128 itself that is 46752, so 31128 is abundant (46752 is more than 31128). Euler's totient φ(31128) = 10368 numbers up to 31128 share no factor with it.
- 4
The digits of 31128 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 41 steps to reach 1.
LaTeX source of the formulas on this page
\[ 31128 = 2^{3} \times 3 \times 1297 \]31128 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 16 |
| Sum of divisors | 77880 |
| Euler totient φ(n) | 10368 |
| Square | 968952384 |
| Cube | 30161549809152 |
| Square root | 176.431290 (= 2√7782) |
| Digit sum / digital root | 15 / 6 |
| Collatz steps to 1 | 41 |
| Scientific notation | 3.1128 × |
31128 in other forms
| Form | Value |
|---|---|
| In words | thirty-one thousand one hundred and twenty-eight |
| Binary (base 2) | 111100110011000 |
| Octal (base 8) | 74630 |
| Hexadecimal (base 16) | 7998 |
| Base 3 | 1120200220 |
| As time | 31128 seconds = 8 h 38 min 48 s |
Is 31128 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (31128 ÷ 2 = 15564) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (31128 ÷ 3 = 10376) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | Yes (31128 ÷ 4 = 7782) | 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 | Yes (31128 ÷ 6 = 5188) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 6) | 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 (31128 ÷ 8 = 3891) | 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 | No (remainder 8) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 9) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | Yes (31128 ÷ 12 = 2594) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 31128 a prime number?
No. 31128 = × 3 × 1297, so it is divisible by 2.
What are the factors of 31128?
1, 2, 3, 4, 6, 8, 12, 24, 1297, 2594, 3891, 5188, 7782, 10376, 15564, 31128.
What is 31128 in binary?
111100110011000 (hexadecimal 7998, octal 74630).
What is the square root of 31128?
About 176.4313, exactly 2√7782.
Is 31128 divisible by 3?
Yes. Its digits add up to 15, a multiple of 3.
What is special about the number 31128?
31128 is a happy number: repeatedly adding the squares of its digits reaches 1.