55
LV
110111
The number 55 — factors and divisors
Deficient
55 = 5 × 11. It has 4 divisors, adding up to 72.
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.
Fibonacci
It sits in the run where each number is the sum of the two before it.
Laid out as dots
It fits as 5 × 11. The more divisors, the closer to a square.
- Prime factors
- 5 × 11
- Divisors
- 1, 5, 11, 55
- Sum of divisors
- 72
- Sum without itself
- 17
- Coprime below it
- 40
- Digit sum
- 10
- Digital root
- 1
- Roman numeral
- LV
- Binary
- 110111
- Octal
- 67
- Hexadecimal
- 37
- Base 36
- 1J
- Bits
- 6 bits
- Collatz steps
- 112 steps · peaks at 9,232
- Prime before
- 53
- Prime after
- 59
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 55 a prime number?
No. It breaks down into 5 × 11.
Q. What are the divisors of 55?
1, 5, 11, 55 — 4 divisors in all, adding up to 72.
Q. How is 55 written in binary?
110111, which is 6 bits. In hexadecimal it is 37.
Q. How many Collatz steps does 55 take?
It reaches 1 in 112, peaking at 9,232 on the way.