Number analysis
1,225
1,225 is a composite odd number that factors as 5^2 × 7^2.
1,225 is a composite odd number that factors as 5^2 × 7^2.
The number itself
- Value
- 1,225
- Digits
- 4
- Digit sum
- 10
- Reversed
- 5,221
- Palindrome
- No
1 + 2 + 2 + 5
Digit sum repeated until one digit remains; equals n mod 9 (with 9 for multiples of 9).
Reverses to 5,221.
Parity and primality
- Parity
- Odd
- Prime
- No
- Prime factorisation
- 5^2 × 7^2
- Squarefree
- No
- Powerful
- Yes
- Möbius μ(n)
- 0
- Nearest primes
- 1,223 ← → 1,229
Leaves remainder 1 on division by 2.
Composite — it factors as 5^2 × 7^2.
2 distinct prime factors, 4 with multiplicity.
At least one prime appears squared.
Every prime factor appears at least squared.
Zero, because a squared prime divides n.
A gap of 6 between them.
Divisors
- Sum of divisors σ(n)
- 1,767
- Aliquot sum
- 542
- Classification
- Deficient
1, 5, 7, 25, 35, 49, 175, 245, 1,225
The proper divisors — everything except n itself.
Its proper divisors fall short by 683.
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
0² + 35² = 1,225 · 21² + 28² = 1,225
Legendre's three-square theorem allows it.
Lagrange's four-square theorem: every non-negative integer is, without exception.
Shapes and sequences
- Triangular number
- Yes — the 49th
- Square number
- Yes — the 35th
- Hexagonal number
- Yes — the 25th
Digit curiosities
- Happy number
- No
- Harshad number
- No
- Collatz trajectory
- 132 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
- 10011001001
- Octal
- 2311
- Hexadecimal
- 4C9
- Base 36
- Y1
- Roman numerals
- MCCXXV
- In words
- one thousand two hundred and twenty-five
- Scientific notation
- 1.225 × 10^3
Is 1,225 a prime number?
Composite — it factors as 5^2 × 7^2.