The number 72101
72101 is a twin prime (72101 and 72103 are both prime) and the 7138th prime number. Its only divisors are 1 and 72101.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 72101: a twin prime (72101 and 72103 are both prime); the 7138th prime number.
- 2
72101 is prime, so its only factors are 1 and 72101. It is the 7138th prime; the next prime is 72103 and the one before is 72091.
- 3
The divisors add up to 72102; without 72101 itself that is 1, so 72101 is deficient (1 is less than 72101). Euler's totient φ(72101) = 72100 numbers up to 72101 share no factor with it.
- 4
The digits of 72101 add up to 11, and repeating that until one digit is left gives the digital root 2. The Collatz sequence (halve if even, else 3n+1) takes 68 steps to reach 1.
72101 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 72102 |
| Euler totient φ(n) | 72100 |
| Square | 5198554201 |
| Cube | 374820956446301 |
| Square root | 268.516294 |
| Digit sum / digital root | 11 / 2 |
| Collatz steps to 1 | 68 |
| Scientific notation | 7.2101 × |
72101 in other forms
| Form | Value |
|---|---|
| In words | seventy-two thousand one hundred and one |
| Binary (base 2) | 10001100110100101 |
| Octal (base 8) | 214645 |
| Hexadecimal (base 16) | 119A5 |
| Base 3 | 10122220102 |
| As time | 72101 seconds = 20 h 1 min 41 s |
Is 72101 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 1) | 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 5) | 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 1) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 7) | 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 72101 a prime number?
Yes. 72101 is divisible only by 1 and itself.
What are the factors of 72101?
1, 72101.
What is 72101 in binary?
10001100110100101 (hexadecimal 119A5, octal 214645).
What is the square root of 72101?
About 268.5163.
Is 72101 divisible by 3?
No. Its digits add up to 11, which is not a multiple of 3.
What is special about the number 72101?
72101 is a twin prime (72101 and 72103 are both prime); the 7138th prime number.