Number analysis
133
133 is a composite odd number that factors as 7 × 19.
133 is a composite odd number that factors as 7 × 19.
The number itself
- Value
- 133
- Digits
- 3
- Digit sum
- 7
- Reversed
- 331
- Palindrome
- No
1 + 3 + 3
Digit sum repeated until one digit remains; equals n mod 9 (with 9 for multiples of 9).
Reverses to 331.
Parity and primality
- Parity
- Odd
- Prime
- No
- Prime factorisation
- 7 × 19
- Squarefree
- Yes
- Semiprime
- Yes
- Möbius μ(n)
- 1
- Nearest primes
- 131 ← → 137
Leaves remainder 1 on division by 2.
Composite — it factors as 7 × 19.
2 distinct prime factors, 2 with multiplicity.
No prime divides it twice.
A product of exactly two primes, counted with multiplicity.
(−1) to the power of 2 distinct prime factors.
A gap of 6 between them.
Divisors
- Aliquot sum
- 27
- Classification
- Deficient
1, 7, 19, 133
The proper divisors — everything except n itself.
Its proper divisors fall short by 106.
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
- Sum of two cubes
- 2³ + 5³
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.
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
- Yes
- Harshad number
- Yes
- Collatz trajectory
- 28 steps to 1
Repeatedly summing the squares of its digits reaches 1.
Divisible by its digit sum 7 — 133 ÷ 7 = 19.
Peaks at 400 along the way.
Written other ways
- Binary
- 10000101
- Octal
- 205
- Hexadecimal
- 85
- Base 36
- 3P
- Roman numerals
- CXXXIII
- In words
- one hundred and thirty-three
- Scientific notation
- 1.33 × 10^2
Is 133 a prime number?
Composite — it factors as 7 × 19.
Nearby numbers
Other numeral systems
Beyond the bases and Roman numerals above, these notations write 133 their own way.
- Morse code
- · − − − − · · · − − · · · − −
- Devanagari
- १३३
- Tamil
- ௱௩௰௩
- Thai
- ๑๓๓
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.