The number 72121
72121 is a composite number with 4 divisors. Its prime factorisation is 7 × 10303. Divisors (4): 1, 7, 10303, 72121.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 72121: a semiprime: 7 × 10303, the product of two primes.
- 2
72121 is composite. Its prime factorisation is
- 3
The divisors add up to 82432; without 72121 itself that is 10311, so 72121 is deficient (10311 is less than 72121). Euler's totient φ(72121) = 61812 numbers up to 72121 share no factor with it.
- 4
The digits of 72121 add up to 13, and repeating that until one digit is left gives the digital root 4. The Collatz sequence (halve if even, else 3n+1) takes 94 steps to reach 1.
LaTeX source of the formulas on this page
\[ 72121 = 7 \times 10303 \]
72121 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 82432 |
| Euler totient φ(n) | 61812 |
| Square | 5201438641 |
| Cube | 375132956227561 |
| Square root | 268.553533 |
| Digit sum / digital root | 13 / 4 |
| Collatz steps to 1 | 94 |
| Scientific notation | 7.2121 × |
72121 in other forms
| Form | Value |
|---|---|
| In words | seventy-two thousand one hundred and twenty-one |
| Binary (base 2) | 10001100110111001 |
| Octal (base 8) | 214671 |
| Hexadecimal (base 16) | 119B9 |
| Base 3 | 10122221011 |
| As time | 72121 seconds = 20 h 2 min 1 s |
Is 72121 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 | Yes (72121 ÷ 7 = 10303) | 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 4) | 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 5) | 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 72121 a prime number?
No. 72121 = 7 × 10303, so it is divisible by 7.
What are the factors of 72121?
1, 7, 10303, 72121.
What is 72121 in binary?
10001100110111001 (hexadecimal 119B9, octal 214671).
What is the square root of 72121?
About 268.5535.
Is 72121 divisible by 3?
No. Its digits add up to 13, which is not a multiple of 3.
What is special about the number 72121?
72121 is a semiprime: 7 × 10303, the product of two primes.