The number 9721
9721 is a twin prime (9719 and 9721 are both prime) and the 1199th prime number. Its only divisors are 1 and 9721.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 9721: a twin prime (9719 and 9721 are both prime); the 1199th prime number.
- 2
9721 is prime, so its only factors are 1 and 9721. It is the 1199th prime; the next prime is 9733 and the one before is 9719.
- 3
The divisors add up to 9722; without 9721 itself that is 1, so 9721 is deficient (1 is less than 9721). Euler's totient φ(9721) = 9720 numbers up to 9721 share no factor with it.
- 4
The digits of 9721 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 166 steps to reach 1.
9721 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 9722 |
| Euler totient φ(n) | 9720 |
| Square | 94497841 |
| Cube | 918613512361 |
| Square root | 98.595132 |
| Digit sum / digital root | 19 / 1 |
| Collatz steps to 1 | 166 |
| Scientific notation | 9.721 × |
9721 in other forms
| Form | Value |
|---|---|
| In words | nine thousand seven hundred and twenty-one |
| Binary (base 2) | 10010111111001 |
| Octal (base 8) | 22771 |
| Hexadecimal (base 16) | 25F9 |
| Base 3 | 111100001 |
| As time | 9721 seconds = 2 h 42 min 1 s |
Is 9721 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 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 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 9721 a prime number?
Yes. 9721 is divisible only by 1 and itself.
What are the factors of 9721?
1, 9721.
What is 9721 in binary?
10010111111001 (hexadecimal 25F9, octal 22771).
What is the square root of 9721?
About 98.5951.
Is 9721 divisible by 3?
No. Its digits add up to 19, which is not a multiple of 3.
What is special about the number 9721?
9721 is a twin prime (9719 and 9721 are both prime); the 1199th prime number.