Number analysis
31,415
The opening digits of π, often used as a placeholder value.
The opening digits of π, often used as a placeholder value.
The number itself
- Value
- 31,415
- Digits
- 5
- Digit sum
- 14
- Reversed
- 51,413
- Palindrome
- No
3 + 1 + 4 + 1 + 5
Digit sum repeated until one digit remains; equals n mod 9 (with 9 for multiples of 9).
Reverses to 51,413.
Parity and primality
- Parity
- Odd
- Prime
- No
- Prime factorisation
- 5 × 61 × 103
- Squarefree
- Yes
- Möbius μ(n)
- -1
- Nearest primes
- 31,397 ← → 31,469
Leaves remainder 1 on division by 2.
Composite — it factors as 5 × 61 × 103.
3 distinct prime factors, 3 with multiplicity.
No prime divides it twice.
(−1) to the power of 3 distinct prime factors.
A gap of 72 between them.
Divisors
- Sum of divisors σ(n)
- 38,688
- Aliquot sum
- 7,273
- Classification
- Deficient
- Euler totient φ(n)
- 24,480
1, 5, 61, 103, 305, 515, 6,283, 31,415
The proper divisors — everything except n itself.
Its proper divisors fall short by 24,142.
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
- Figurate shapes
- None
Not triangular, square, pentagonal, hexagonal, cubic, Fibonacci, Lucas, Catalan, factorial or a power of two.
Digit curiosities
- Happy number
- No
- Harshad number
- No
- Collatz trajectory
- 85 steps to 1
Summing the squares of its digits falls into the 4 → 16 → 37 → … → 4 cycle.
Not divisible by its digit sum 14.
Peaks at 212,056 along the way.
Written other ways
- Binary
- 111101010110111
- Octal
- 75267
- Hexadecimal
- 7AB7
- Base 36
- O8N
- In words
- thirty-one thousand four hundred and fifteen
- Scientific notation
- 3.1415 × 10^4
Standard Roman numerals only run from 1 to 3,999.
Is 31,415 a prime number?
Composite — it factors as 5 × 61 × 103.