Number analysis
145
145 is a composite odd number that factors as 5 × 29.
145 is a composite odd number that factors as 5 × 29.
The number itself
- Value
- 145
- Digits
- 3
- Digit sum
- 10
- Reversed
- 541
- Palindrome
- No
1 + 4 + 5
Digit sum repeated until one digit remains; equals n mod 9 (with 9 for multiples of 9).
Reverses to 541.
Parity and primality
- Parity
- Odd
- Prime
- No
- Prime factorisation
- 5 × 29
- Squarefree
- Yes
- Semiprime
- Yes
- Möbius μ(n)
- 1
- Nearest primes
- 139 ← → 149
Leaves remainder 1 on division by 2.
Composite — it factors as 5 × 29.
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 10 between them.
Divisors
- Aliquot sum
- 35
- Classification
- Deficient
1, 5, 29, 145
The proper divisors — everything except n itself.
Its proper divisors fall short by 110.
How many integers from 1 to n share no factor with n.
Sums and additive structure
- Sum of two squares
- Yes
- Sum of three squares
- Yes
- Sum of four squares
- Yes
1² + 12² = 145 · 8² + 9² = 145
Legendre's three-square theorem allows it.
Lagrange's four-square theorem: every non-negative integer is, without exception.
Shapes and sequences
- Pentagonal number
- Yes — the 10th
Digit curiosities
- Happy number
- No
- Harshad number
- No
- Collatz trajectory
- 116 steps to 1
Summing the squares of its digits falls into the 4 → 16 → 37 → … → 4 cycle.
Not divisible by its digit sum 10.
Peaks at 9,232 along the way.
Written other ways
- Binary
- 10010001
- Octal
- 221
- Hexadecimal
- 91
- Base 36
- 41
- Roman numerals
- CXLV
- In words
- one hundred and forty-five
- Scientific notation
- 1.45 × 10^2
Is 145 a prime number?
Composite — it factors as 5 × 29.
Nearby numbers
Other numeral systems
Beyond the bases and Roman numerals above, these notations write 145 their own way.
- Morse code
- · − − − − · · · · − · · · · ·
- Devanagari
- १४५
- Tamil
- ௱௪௰௫
- Thai
- ๑๔๕
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.