The number 61991
61991 is the 6232nd prime number. Its only divisors are 1 and 61991.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 61991: the 6232nd prime number.
- 2
61991 is prime, so its only factors are 1 and 61991. It is the 6232nd prime; the next prime is 62003 and the one before is 61987.
- 3
The divisors add up to 61992; without 61991 itself that is 1, so 61991 is deficient (1 is less than 61991). Euler's totient φ(61991) = 61990 numbers up to 61991 share no factor with it.
- 4
The digits of 61991 add up to 26, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 117 steps to reach 1.
61991 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 61992 |
| Euler totient φ(n) | 61990 |
| Square | 3842884081 |
| Cube | 238224227065271 |
| Square root | 248.979919 |
| Digit sum / digital root | 26 / 8 |
| Collatz steps to 1 | 117 |
| Scientific notation | 6.1991 × |
61991 in other forms
| Form | Value |
|---|---|
| In words | sixty-one thousand nine hundred and ninety-one |
| Binary (base 2) | 1111001000100111 |
| Octal (base 8) | 171047 |
| Hexadecimal (base 16) | F227 |
| Base 3 | 10011000222 |
| As time | 61991 seconds = 17 h 13 min 11 s |
Is 61991 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 3) | 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 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 7) | 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 6) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 11) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 61991 a prime number?
Yes. 61991 is divisible only by 1 and itself.
What are the factors of 61991?
1, 61991.
What is 61991 in binary?
1111001000100111 (hexadecimal F227, octal 171047).
What is the square root of 61991?
About 248.9799.
Is 61991 divisible by 3?
No. Its digits add up to 26, which is not a multiple of 3.
What is special about the number 61991?
61991 is the 6232nd prime number.