The number 72161
72161 is the 7142nd prime number. Its only divisors are 1 and 72161.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 72161: the 7142nd prime number; a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
72161 is prime, so its only factors are 1 and 72161. It is the 7142nd prime; the next prime is 72167 and the one before is 72139.
- 3
The divisors add up to 72162; without 72161 itself that is 1, so 72161 is deficient (1 is less than 72161). Euler's totient φ(72161) = 72160 numbers up to 72161 share no factor with it.
- 4
The digits of 72161 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 81 steps to reach 1.
72161 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 72162 |
| Euler totient φ(n) | 72160 |
| Square | 5207209921 |
| Cube | 375757475109281 |
| Square root | 268.627996 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 81 |
| Scientific notation | 7.2161 × |
72161 in other forms
| Form | Value |
|---|---|
| In words | seventy-two thousand one hundred and sixty-one |
| Binary (base 2) | 10001100111100001 |
| Octal (base 8) | 214741 |
| Hexadecimal (base 16) | 119E1 |
| Base 3 | 10122222122 |
| As time | 72161 seconds = 20 h 2 min 41 s |
Is 72161 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 1) | 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 5) | 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 8) | 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 5) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 72161 a prime number?
Yes. 72161 is divisible only by 1 and itself.
What are the factors of 72161?
1, 72161.
What is 72161 in binary?
10001100111100001 (hexadecimal 119E1, octal 214741).
What is the square root of 72161?
About 268.6280.
Is 72161 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 72161?
72161 is the 7142nd prime number; a happy number: repeatedly adding the squares of its digits reaches 1.