The number 72129
72129 is a composite number with 4 divisors. Its prime factorisation is 3 × 24043. Divisors (4): 1, 3, 24043, 72129.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 72129: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 24043, the product of two primes.
- 2
72129 is composite. Its prime factorisation is
- 3
The divisors add up to 96176; without 72129 itself that is 24047, so 72129 is deficient (24047 is less than 72129). Euler's totient φ(72129) = 48084 numbers up to 72129 share no factor with it.
- 4
The digits of 72129 add up to 21, and repeating that until one digit is left gives the digital root 3. The Collatz sequence (halve if even, else 3n+1) takes 125 steps to reach 1.
LaTeX source of the formulas on this page
\[ 72129 = 3 \times 24043 \]
72129 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 96176 |
| Euler totient φ(n) | 48084 |
| Square | 5202592641 |
| Cube | 375257804602689 |
| Square root | 268.568427 |
| Digit sum / digital root | 21 / 3 |
| Collatz steps to 1 | 125 |
| Scientific notation | 7.2129 × |
72129 in other forms
| Form | Value |
|---|---|
| In words | seventy-two thousand one hundred and twenty-nine |
| Binary (base 2) | 10001100111000001 |
| Octal (base 8) | 214701 |
| Hexadecimal (base 16) | 119C1 |
| Base 3 | 10122221110 |
| As time | 72129 seconds = 20 h 2 min 9 s |
Is 72129 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 | Yes (72129 ÷ 3 = 24043) | 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 4) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | 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 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 3) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 9) | A number is divisible by 10 if the last digit is 0. |
| 11 | No (remainder 2) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 72129 a prime number?
No. 72129 = 3 × 24043, so it is divisible by 3.
What are the factors of 72129?
1, 3, 24043, 72129.
What is 72129 in binary?
10001100111000001 (hexadecimal 119C1, octal 214701).
What is the square root of 72129?
About 268.5684.
Is 72129 divisible by 3?
Yes. Its digits add up to 21, a multiple of 3.
What is special about the number 72129?
72129 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 3 × 24043, the product of two primes.