The number 31987
31987 is a composite number with 4 divisors. Its prime factorisation is 29 × 1103. Divisors (4): 1, 29, 1103, 31987.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 31987: a semiprime: 29 × 1103, the product of two primes.
- 2
31987 is composite. Its prime factorisation is
- 3
The divisors add up to 33120; without 31987 itself that is 1133, so 31987 is deficient (1133 is less than 31987). Euler's totient φ(31987) = 30856 numbers up to 31987 share no factor with it.
- 4
The digits of 31987 add up to 28, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 191 steps to reach 1.
LaTeX source of the formulas on this page
\[ 31987 = 29 \times 1103 \]
31987 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 33120 |
| Euler totient φ(n) | 30856 |
| Square | 1023168169 |
| Cube | 32728080221803 |
| Square root | 178.849098 |
| Digit sum / digital root | 28 / 1 |
| Collatz steps to 1 | 191 |
| Scientific notation | 3.1987 × |
31987 in other forms
| Form | Value |
|---|---|
| In words | thirty-one thousand nine hundred and eighty-seven |
| Binary (base 2) | 111110011110011 |
| Octal (base 8) | 76363 |
| Hexadecimal (base 16) | 7CF3 |
| Base 3 | 1121212201 |
| As time | 31987 seconds = 8 h 53 min 7 s |
Is 31987 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 3) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 2) | 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 4) | 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 3) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 1) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 7) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 10) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 7) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 31987 a prime number?
No. 31987 = 29 × 1103, so it is divisible by 29.
What are the factors of 31987?
1, 29, 1103, 31987.
What is 31987 in binary?
111110011110011 (hexadecimal 7CF3, octal 76363).
What is the square root of 31987?
About 178.8491.
Is 31987 divisible by 3?
No. Its digits add up to 28, which is not a multiple of 3.
What is special about the number 31987?
31987 is a semiprime: 29 × 1103, the product of two primes.