231
CCXXXI
11100111
The number 231 — factors and divisors
Deficient
231 = 3 × 7 × 11. It has 8 divisors, adding up to 384.
Its divisors, itself excluded, add up to less than the number.
Families it belongs to
Triangular
The running total of 1, 2, 3 … — the dots stack into a triangle.
Laid out as dots
It fits as 11 × 21. The more divisors, the closer to a square.
- Prime factors
- 3 × 7 × 11
- Divisors
- 1, 3, 7, 11, 21, 33, 77, 231
- Sum of divisors
- 384
- Sum without itself
- 153
- Coprime below it
- 120
- Digit sum
- 6
- Digital root
- 6
- Roman numeral
- CCXXXI
- Binary
- 11100111
- Octal
- 347
- Hexadecimal
- E7
- Base 36
- 6F
- Bits
- 8 bits
- Collatz steps
- 127 steps · peaks at 9,232
- Prime before
- 229
- Prime after
- 233
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 231 a prime number?
No. It breaks down into 3 × 7 × 11.
Q. What are the divisors of 231?
1, 3, 7, 11, 21, 33, 77, 231 — 8 divisors in all, adding up to 384.
Q. How is 231 written in binary?
11100111, which is 8 bits. In hexadecimal it is E7.
Q. How many Collatz steps does 231 take?
It reaches 1 in 127, peaking at 9,232 on the way.