The number 81001
81001 is the 7926th prime number. Its only divisors are 1 and 81001.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81001: the 7926th prime number.
- 2
81001 is prime, so its only factors are 1 and 81001. It is the 7926th prime; the next prime is 81013 and the one before is 80989.
- 3
The divisors add up to 81002; without 81001 itself that is 1, so 81001 is deficient (1 is less than 81001). Euler's totient φ(81001) = 81000 numbers up to 81001 share no factor with it.
- 4
The digits of 81001 add up to 10, and repeating that until one digit is left gives the digital root 1. The Collatz sequence (halve if even, else 3n+1) takes 213 steps to reach 1.
81001 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 81002 |
| Euler totient φ(n) | 81000 |
| Square | 6561162001 |
| Cube | 531460683243001 |
| Square root | 284.606746 |
| Digit sum / digital root | 10 / 1 |
| Collatz steps to 1 | 213 |
| Scientific notation | 8.1001 × |
81001 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand and one |
| Binary (base 2) | 10011110001101001 |
| Octal (base 8) | 236151 |
| Hexadecimal (base 16) | 13C69 |
| Base 3 | 11010010001 |
| As time | 81001 seconds = 22 h 30 min 1 s |
Is 81001 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 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 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 8) | 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 81001 a prime number?
Yes. 81001 is divisible only by 1 and itself.
What are the factors of 81001?
1, 81001.
What is 81001 in binary?
10011110001101001 (hexadecimal 13C69, octal 236151).
What is the square root of 81001?
About 284.6067.
Is 81001 divisible by 3?
No. Its digits add up to 10, which is not a multiple of 3.
What is special about the number 81001?
81001 is the 7926th prime number.