The number 21210
21210 is a composite number with 32 divisors. Its prime factorisation is 2 × 3 × 5 × 7 × 101. Divisors (32): 1, 2, 3, 5, 6, 7, 10, 14, 15, 21, 30, 35, 42, 70, 101, 105 … 21210.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 21210: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 6.
- 2
21210 is composite. Its prime factorisation is
- 3
The divisors add up to 58752; without 21210 itself that is 37542, so 21210 is abundant (37542 is more than 21210). Euler's totient φ(21210) = 4800 numbers up to 21210 share no factor with it.
- 4
The digits of 21210 add up to 6, and repeating that until one digit is left gives the digital root 6. The Collatz sequence (halve if even, else 3n+1) takes 149 steps to reach 1.
LaTeX source of the formulas on this page
\[ 21210 = 2 \times 3 \times 5 \times 7 \times 101 \]
21210 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 32 |
| Sum of divisors | 58752 |
| Euler totient φ(n) | 4800 |
| Square | 449864100 |
| Cube | 9541617561000 |
| Square root | 145.636534 |
| Digit sum / digital root | 6 / 6 |
| Collatz steps to 1 | 149 |
| Scientific notation | 2.121 × |
21210 in other forms
| Form | Value |
|---|---|
| In words | twenty-one thousand two hundred and ten |
| Binary (base 2) | 101001011011010 |
| Octal (base 8) | 51332 |
| Hexadecimal (base 16) | 52DA |
| Base 3 | 1002002120 |
| As time | 21210 seconds = 5 h 53 min 30 s |
Is 21210 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (21210 ÷ 2 = 10605) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (21210 ÷ 3 = 7070) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (21210 ÷ 5 = 4242) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | Yes (21210 ÷ 6 = 3535) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (21210 ÷ 7 = 3030) | 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 2) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 6) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (21210 ÷ 10 = 2121) | 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 6) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 21210 a prime number?
No. 21210 = 2 × 3 × 5 × 7 × 101, so it is divisible by 2.
What are the factors of 21210?
1, 2, 3, 5, 6, 7, 10, 14, 15, 21, 30, 35, 42, 70, 101, 105, 202, 210, 303, 505, 606, 707, 1010, 1414, 1515, 2121, 3030, 3535, 4242, 7070, 10605, 21210.
What is 21210 in binary?
101001011011010 (hexadecimal 52DA, octal 51332).
What is the square root of 21210?
About 145.6365.
Is 21210 divisible by 3?
Yes. Its digits add up to 6, a multiple of 3.
What is special about the number 21210?
21210 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 6.