Number reference
70 explained.
70: seventy, composite; factors, prime factorization, roots, binary, hexadecimal, and digit properties.
Identity and representations
- Written form
- seventy
- Classification
- composite
- Factors
- 1, 2, 5, 7, 10, 14, 35, 70
- Prime factorization
- 2 × 5 × 7
- Square root
- 8.3666
- Cube root
- 4.121285
- Binary
- 1000110
- Octal
- 106
- Hexadecimal
- 46
- Roman numeral
- LXX
- Digit sum
- 7
- Digital root
- 7
What makes 70 notable
- Factor structure. 70 breaks down into 3 distinct primes (2, 5, 7) and has 8 divisors in total, so it can be split into equal whole-number groups 6 ways beyond 1 and itself.
70 in everyday use
Seventy miles per hour is the national speed limit on British motorways, fixed in 1965. It is the atomic number of ytterbium, a rare earth used in some atomic clocks and fibre lasers. A seventieth anniversary is platinum. "Threescore years and ten" is the lifespan named in Psalm 90, and 70 percent ethanol is the standard concentration for disinfectant. The 1970s gave their name to a decade of fashion and music.
Seventy is 2 × 5 × 7 and the smallest weird number: it is abundant, with proper divisors summing to 74, yet no subset of those divisors adds up to exactly 70. It is a pentagonal number, following 51, and the central entry of the eighth row of Pascal's triangle, the number of ways to choose four items from eight. In binary it is 1000110.
Nearby numbers
How to read this page
The factor list shows every way 70 splits into equal whole-number groups — 8 divisors in total. The prime factorisation is the compact form of that same information, and the base conversions restate 70 for contexts that do not use decimal.
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