The number 7121
7121 is the 912th prime number. Its only divisors are 1 and 7121.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 7121: the 912th prime number.
- 2
7121 is prime, so its only factors are 1 and 7121. It is the 912th prime; the next prime is 7127 and the one before is 7109.
- 3
The divisors add up to 7122; without 7121 itself that is 1, so 7121 is deficient (1 is less than 7121). Euler's totient φ(7121) = 7120 numbers up to 7121 share no factor with it.
- 4
The digits of 7121 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 150 steps to reach 1.
7121 at a glance
| Property | Value |
|---|---|
| Type | prime |
| Number of divisors | 2 |
| Sum of divisors | 7122 |
| Euler totient φ(n) | 7120 |
| Square | 50708641 |
| Cube | 361096232561 |
| Square root | 84.386018 |
| Digit sum / digital root | 11 / 2 |
| Collatz steps to 1 | 150 |
| Scientific notation | 7.121 × |
7121 in other forms
| Form | Value |
|---|---|
| In words | seven thousand one hundred and twenty-one |
| Binary (base 2) | 1101111010001 |
| Octal (base 8) | 15721 |
| Hexadecimal (base 16) | 1BD1 |
| Base 3 | 100202202 |
| As time | 7121 seconds = 1 h 58 min 41 s |
Is 7121 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 2) | 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 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 4) | 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 7121 a prime number?
Yes. 7121 is divisible only by 1 and itself.
What are the factors of 7121?
1, 7121.
What is 7121 in binary?
1101111010001 (hexadecimal 1BD1, octal 15721).
What is the square root of 7121?
About 84.3860.
Is 7121 divisible by 3?
No. Its digits add up to 11, which is not a multiple of 3.
What is special about the number 7121?
7121 is the 912th prime number.