The number 87121
87121 is a twin prime (87119 and 87121 are both prime) and the 8461st prime number. Its only divisors are 1 and 87121.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 87121: a twin prime (87119 and 87121 are both prime); the 8461st prime number.
- 2
87121 is prime, so its only factors are 1 and 87121. It is the 8461st prime; the next prime is 87133 and the one before is 87119.
- 3
The divisors add up to 87122; without 87121 itself that is 1, so 87121 is deficient (1 is less than 87121). Euler's totient φ(87121) = 87120 numbers up to 87121 share no factor with it.
- 4
The digits of 87121 add up to 19, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 164 steps to reach 1.
87121 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 87122 |
| Euler totient φ(n) | 87120 |
| Square | 7590068641 |
| Cube | 661254370072561 |
| Square root | 295.162667 |
| Digit sum / digital root | 19 / 1 |
| Collatz steps to 1 | 164 |
| Scientific notation | 8.7121 × |
87121 in other forms
| Form | Value |
|---|---|
| In words | eighty-seven thousand one hundred and twenty-one |
| Binary (base 2) | 10101010001010001 |
| Octal (base 8) | 252121 |
| Hexadecimal (base 16) | 15451 |
| Base 3 | 11102111201 |
| As time | 87121 seconds = 24 h 12 min 1 s |
Is 87121 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 1) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 1) | 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 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 | No (remainder 1) | 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 1) | 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 | No (remainder 1) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 87121 a prime number?
Yes. 87121 is divisible only by 1 and itself.
What are the factors of 87121?
1, 87121.
What is 87121 in binary?
10101010001010001 (hexadecimal 15451, octal 252121).
What is the square root of 87121?
About 295.1627.
Is 87121 divisible by 3?
No. Its digits add up to 19, which is not a multiple of 3.
What is special about the number 87121?
87121 is a twin prime (87119 and 87121 are both prime); the 8461st prime number.