99
XCIX
1100011
The number 99 — factors and divisors
Deficient
99 = 3² × 11. It has 6 divisors, adding up to 156.
Its divisors, itself excluded, add up to less than the number.
Laid out as dots
It fits as 9 × 11. The more divisors, the closer to a square.
- Prime factors
- 3² × 11
- Divisors
- 1, 3, 9, 11, 33, 99
- Sum of divisors
- 156
- Sum without itself
- 57
- Coprime below it
- 60
- Digit sum
- 18
- Digital root
- 9
- Roman numeral
- XCIX
- Binary
- 1100011
- Octal
- 143
- Hexadecimal
- 63
- Base 36
- 2R
- Bits
- 7 bits
- Collatz steps
- 25 steps · peaks at 448
- Prime before
- 97
- Prime after
- 101
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 99 a prime number?
No. It breaks down into 3² × 11.
Q. What are the divisors of 99?
1, 3, 9, 11, 33, 99 — 6 divisors in all, adding up to 156.
Q. How is 99 written in binary?
1100011, which is 7 bits. In hexadecimal it is 63.
Q. How many Collatz steps does 99 take?
It reaches 1 in 25, peaking at 448 on the way.