Number analysis
47
47 is a prime number — divisible only by 1 and itself.
47 is a prime number — divisible only by 1 and itself.
The number itself
- Value
- 47
- Digits
- 2
- Digit sum
- 11
- Reversed
- 74
- Palindrome
- No
4 + 7
Digit sum repeated until one digit remains; equals n mod 9 (with 9 for multiples of 9).
Reverses to 74.
Parity and primality
- Parity
- Odd
- Prime
- Yes
- Squarefree
- Yes
- Möbius μ(n)
- -1
- Nearest primes
- 43 ← → 53
Leaves remainder 1 on division by 2.
Divisible only by 1 and itself.
1 distinct prime factor, 1 with multiplicity.
No prime divides it twice.
(−1) to the power of 1 distinct prime factors.
A gap of 10 between them.
Divisors
- Aliquot sum
- 1
- Classification
- Deficient
1, 47
The proper divisors — everything except n itself.
Its proper divisors fall short by 46.
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
- No
- Sum of four squares
- Yes
A prime congruent to 3 mod 4 divides it an odd number of times, which rules it out.
Excluded by Legendre: it has the form 4^a(8b + 7).
Lagrange's four-square theorem: every non-negative integer is, without exception.
Shapes and sequences
- Lucas number
- Yes — index 8
Digit curiosities
- Happy number
- No
- Harshad number
- No
- Collatz trajectory
- 104 steps to 1
Summing the squares of its digits falls into the 4 → 16 → 37 → … → 4 cycle.
Not divisible by its digit sum 11.
Peaks at 9,232 along the way.
Written other ways
- Binary
- 101111
- Octal
- 57
- Hexadecimal
- 2F
- Base 36
- 1B
- Roman numerals
- XLVII
- In words
- forty-seven
- Scientific notation
- 4.7 × 10^1
Is 47 a prime number?
Yes. 47 has no divisors other than 1 and itself.
Nearby numbers
Other numeral systems
Beyond the bases and Roman numerals above, these notations write 47 their own way.
- Greek (alphabetic)
- ΜΖʹ
- Babylonian cuneiform
- 𒐏𒐛
- Tamil
- ௪௰௭
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.