225
CCXXV
11100001
The number 225 — factors and divisors
Deficient
225 = 3² × 5². It has 9 divisors, adding up to 403.
Its divisors, itself excluded, add up to less than the number.
Families it belongs to
Square
A number times itself — the dots lay out as a square.
Laid out as dots
It fits as 15 × 15. The more divisors, the closer to a square.
- Prime factors
- 3² × 5²
- Divisors
- 1, 3, 5, 9, 15, 25, 45, 75, 225
- Sum of divisors
- 403
- Sum without itself
- 178
- Coprime below it
- 120
- Digit sum
- 9
- Digital root
- 9
- Roman numeral
- CCXXV
- Binary
- 11100001
- Octal
- 341
- Hexadecimal
- E1
- Base 36
- 69
- Bits
- 8 bits
- Collatz steps
- 52 steps · peaks at 4,372
- Prime before
- 223
- Prime after
- 227
The grid
Ten per row, twenty rows. The filled cells are primes — you can see the multiples of 2 and 5 drop out in columns.
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Numbers either side
How to read this
- The prime factors are what the number is made of. The count and sum of divisors both follow from them.
- Add the divisors, take the number away, and you get perfect, abundant or deficient.
- The length of the binary form is the bit count. 255 taking eight digits is what a byte is.
- Collatz: halve it if even, triple it and add one if odd. The count is how many moves reach 1.
Frequently asked questions
Q. Is 225 a prime number?
No. It breaks down into 3² × 5².
Q. What are the divisors of 225?
1, 3, 5, 9, 15, 25, 45, 75, 225 — 9 divisors in all, adding up to 403.
Q. How is 225 written in binary?
11100001, which is 8 bits. In hexadecimal it is E1.
Q. How many Collatz steps does 225 take?
It reaches 1 in 52, peaking at 4,372 on the way.