90
XC
1011010
The number 90 — factors and divisors
Abundant
90 = 2 × 3² × 5. It has 12 divisors, adding up to 234.
Its divisors, itself excluded, add up to more than the number.
Laid out as dots
It fits as 9 × 10. The more divisors, the closer to a square.
- Prime factors
- 2 × 3² × 5
- Divisors
- 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90
- Sum of divisors
- 234
- Sum without itself
- 144
- Coprime below it
- 24
- Digit sum
- 9
- Digital root
- 9
- Roman numeral
- XC
- Binary
- 1011010
- Octal
- 132
- Hexadecimal
- 5A
- Base 36
- 2I
- Bits
- 7 bits
- Collatz steps
- 17 steps · peaks at 136
- Prime before
- 89
- Prime after
- 97
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 90 a prime number?
No. It breaks down into 2 × 3² × 5.
Q. What are the divisors of 90?
1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90 — 12 divisors in all, adding up to 234.
Q. How is 90 written in binary?
1011010, which is 7 bits. In hexadecimal it is 5A.
Q. How many Collatz steps does 90 take?
It reaches 1 in 17, peaking at 136 on the way.