The number 70721
70721 is a composite number with 4 divisors. Its prime factorisation is 7 × 10103. Divisors (4): 1, 7, 10103, 70721.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 70721: a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 7 × 10103, the product of two primes.
- 2
70721 is composite. Its prime factorisation is
- 3
The divisors add up to 80832; without 70721 itself that is 10111, so 70721 is deficient (10111 is less than 70721). Euler's totient φ(70721) = 60612 numbers up to 70721 share no factor with it.
- 4
The digits of 70721 add up to 17, and repeating that until one digit is left gives the digital root 8. The Collatz sequence (halve if even, else 3n+1) takes 81 steps to reach 1.
LaTeX source of the formulas on this page
\[ 70721 = 7 \times 10103 \]
70721 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 4 |
| Sum of divisors | 80832 |
| Euler totient φ(n) | 60612 |
| Square | 5001459841 |
| Cube | 353708241415361 |
| Square root | 265.934202 |
| Digit sum / digital root | 17 / 8 |
| Collatz steps to 1 | 81 |
| Scientific notation | 7.0721 × |
70721 in other forms
| Form | Value |
|---|---|
| In words | seventy thousand seven hundred and twenty-one |
| Binary (base 2) | 10001010001000001 |
| Octal (base 8) | 212101 |
| Hexadecimal (base 16) | 11441 |
| Base 3 | 10121000022 |
| As time | 70721 seconds = 19 h 38 min 41 s |
Is 70721 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 | Yes (70721 ÷ 7 = 10103) | 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 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 2) | 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 70721 a prime number?
No. 70721 = 7 × 10103, so it is divisible by 7.
What are the factors of 70721?
1, 7, 10103, 70721.
What is 70721 in binary?
10001010001000001 (hexadecimal 11441, octal 212101).
What is the square root of 70721?
About 265.9342.
Is 70721 divisible by 3?
No. Its digits add up to 17, which is not a multiple of 3.
What is special about the number 70721?
70721 is a happy number: repeatedly adding the squares of its digits reaches 1; a semiprime: 7 × 10103, the product of two primes.