The number 857
857 is a twin prime (857 and 859 are both prime) and the 148th prime number. Its only divisors are 1 and 857.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 857: a twin prime (857 and 859 are both prime); the 148th prime number.
- 2
857 is prime, so its only factors are 1 and 857. It is the 148th prime; the next prime is 859 and the one before is 853.
- 3
The divisors add up to 858; without 857 itself that is 1, so 857 is deficient (1 is less than 857). Euler's totient φ(857) = 856 numbers up to 857 share no factor with it.
- 4
The digits of 857 add up to 20, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 28 steps to reach 1.
857 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 858 |
| Euler totient φ(n) | 856 |
| Square | 734449 |
| Cube | 629422793 |
| Square root | 29.274562 |
| Digit sum / digital root | 20 / 2 |
| Collatz steps to 1 | 28 |
| Scientific notation | 8.57 × |
857 in other forms
| Form | Value |
|---|---|
| In words | eight hundred and fifty-seven |
| Roman numerals | DCCCLVII |
| Binary (base 2) | 1101011001 |
| Octal (base 8) | 1531 |
| Hexadecimal (base 16) | 359 |
| Base 3 | 1011202 |
| As time | 857 seconds = 14 min 17 s |
Is 857 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 2) | 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 2) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 5) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | No (remainder 3) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 2) | 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 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 857 a prime number?
Yes. 857 is divisible only by 1 and itself.
What are the factors of 857?
1, 857.
What is 857 in binary?
1101011001 (hexadecimal 359, octal 1531).
What is the square root of 857?
About 29.2746.
What is 857 in Roman numerals?
DCCCLVII.
Is 857 divisible by 3?
No. Its digits add up to 20, which is not a multiple of 3.
What is special about the number 857?
857 is a twin prime (857 and 859 are both prime); the 148th prime number.