66
LXVI
1000010
The number 66 — factors and divisors
Abundant
66 = 2 × 3 × 11. It has 8 divisors, adding up to 144.
Its divisors, itself excluded, add up to more 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 6 × 11. The more divisors, the closer to a square.
- Prime factors
- 2 × 3 × 11
- Divisors
- 1, 2, 3, 6, 11, 22, 33, 66
- Sum of divisors
- 144
- Sum without itself
- 78
- Coprime below it
- 20
- Digit sum
- 12
- Digital root
- 3
- Roman numeral
- LXVI
- Binary
- 1000010
- Octal
- 102
- Hexadecimal
- 42
- Base 36
- 1U
- Bits
- 7 bits
- Collatz steps
- 27 steps · peaks at 100
- Prime before
- 61
- Prime after
- 67
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 66 a prime number?
No. It breaks down into 2 × 3 × 11.
Q. What are the divisors of 66?
1, 2, 3, 6, 11, 22, 33, 66 — 8 divisors in all, adding up to 144.
Q. How is 66 written in binary?
1000010, which is 7 bits. In hexadecimal it is 42.
Q. How many Collatz steps does 66 take?
It reaches 1 in 27, peaking at 100 on the way.