Number analysis
70
70 is a composite even number that factors as 2 × 5 × 7.
70 is a composite even number that factors as 2 × 5 × 7.
The number itself
- Value
- 70
- Digits
- 2
- Digit sum
- 7
- Reversed
- 7
- Palindrome
- No
7 + 0
Digit sum repeated until one digit remains; equals n mod 9 (with 9 for multiples of 9).
Reverses to 7.
Parity and primality
- Parity
- Even
- Prime
- No
- Prime factorisation
- 2 × 5 × 7
- Squarefree
- Yes
- Möbius μ(n)
- -1
- Nearest primes
- 67 ← → 71
Divisible by 2.
Composite — it factors as 2 × 5 × 7.
3 distinct prime factors, 3 with multiplicity.
No prime divides it twice.
(−1) to the power of 3 distinct prime factors.
A gap of 4 between them.
Divisors
- Aliquot sum
- 74
- Classification
- Abundant
1, 2, 5, 7, 10, 14, 35, 70
The proper divisors — everything except n itself.
Its proper divisors overshoot by 4.
How many integers from 1 to n share no factor with n.
Sums and additive structure
- Sum of two squares
- No
- Sum of three squares
- Yes
- Sum of four squares
- Yes
- Goldbach pair
- 3 + 67
A prime congruent to 3 mod 4 divides it an odd number of times, which rules it out.
Legendre's three-square theorem allows it.
Lagrange's four-square theorem: every non-negative integer is, without exception.
The smallest pair of primes summing to n. Goldbach’s conjecture says one always exists; it remains unproven.
Shapes and sequences
- Pentagonal number
- Yes — the 7th
Digit curiosities
- Happy number
- Yes
- Harshad number
- Yes
- Collatz trajectory
- 14 steps to 1
Repeatedly summing the squares of its digits reaches 1.
Divisible by its digit sum 7 — 70 ÷ 7 = 10.
Peaks at 160 along the way.
Written other ways
- Binary
- 1000110
- Octal
- 106
- Hexadecimal
- 46
- Base 36
- 1Y
- Roman numerals
- LXX
- In words
- seventy
- Scientific notation
- 7.0 × 10^1
Is 70 a prime number?
Composite — it factors as 2 × 5 × 7.
Nearby numbers
Other numeral systems
Beyond the bases and Roman numerals above, these notations write 70 their own way.
- Greek (alphabetic)
- Οʹ
- Babylonian cuneiform
- 𒐕𒌋
- Tamil
- ௭௰
References
Further reading: Wikipedia · Wikidata
Notations, naming and the links above come from Wikidata, whose structured data is dedicated to the public domain under CC0-1.0. Retrieved 2026-10-07.