213
CCXIII
11010101
The number 213 — factors and divisors
Deficient
213 = 3 × 71. It has 4 divisors, adding up to 288.
Its divisors, itself excluded, add up to less than the number.
Laid out as dots
It fits as 3 × 71. The more divisors, the closer to a square.
- Prime factors
- 3 × 71
- Divisors
- 1, 3, 71, 213
- Sum of divisors
- 288
- Sum without itself
- 75
- Coprime below it
- 140
- Digit sum
- 6
- Digital root
- 6
- Roman numeral
- CCXIII
- Binary
- 11010101
- Octal
- 325
- Hexadecimal
- D5
- Base 36
- 5X
- Bits
- 8 bits
- Collatz steps
- 13 steps · peaks at 640
- Prime before
- 211
- Prime after
- 223
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 213 a prime number?
No. It breaks down into 3 × 71.
Q. What are the divisors of 213?
1, 3, 71, 213 — 4 divisors in all, adding up to 288.
Q. How is 213 written in binary?
11010101, which is 8 bits. In hexadecimal it is D5.
Q. How many Collatz steps does 213 take?
It reaches 1 in 13, peaking at 640 on the way.