The number 70
70 is a composite number with 8 divisors. Its prime factorisation is 2 × 5 × 7. Divisors (8): 1, 2, 5, 7, 10, 14, 35, 70.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 70: a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 7.
- 2
70 is composite. Its prime factorisation is
- 3
The divisors add up to 144; without 70 itself that is 74, so 70 is abundant (74 is more than 70). Euler's totient φ(70) = 24 numbers up to 70 share no factor with it.
- 4
The digits of 70 add up to 7, and repeating that until one digit is left gives the digital root 7. The Collatz sequence (halve if even, else 3n+1) takes 14 steps to reach 1.
LaTeX source of the formulas on this page
\[ 70 = 2 \times 5 \times 7 \]
70 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 8 |
| Sum of divisors | 144 |
| Euler totient φ(n) | 24 |
| Square | 4900 |
| Cube | 343000 |
| Square root | 8.366600 |
| Digit sum / digital root | 7 / 7 |
| Collatz steps to 1 | 14 |
| Scientific notation | 7 × |
70 in other forms
| Form | Value |
|---|---|
| In words | seventy |
| Roman numerals | LXX |
| Binary (base 2) | 1000110 |
| Octal (base 8) | 106 |
| Hexadecimal (base 16) | 46 |
| Base 3 | 2121 |
| As time | 70 seconds = 1 min 10 s |
Is 70 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | Yes (70 ÷ 2 = 35) | 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 2) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | Yes (70 ÷ 5 = 14) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 4) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (70 ÷ 7 = 10) | 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 6) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | No (remainder 7) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | Yes (70 ÷ 10 = 7) | 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 10) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 70 a prime number?
No. 70 = 2 × 5 × 7, so it is divisible by 2.
What are the factors of 70?
1, 2, 5, 7, 10, 14, 35, 70.
What is 70 in binary?
1000110 (hexadecimal 46, octal 106).
What is the square root of 70?
About 8.3666.
What is 70 in Roman numerals?
LXX.
Is 70 divisible by 3?
No. Its digits add up to 7, which is not a multiple of 3.
What is special about the number 70?
70 is a happy number: repeatedly adding the squares of its digits reaches 1; a Harshad number: divisible by its digit sum 7.