65
LXV
1000001
The number 65 — factors and divisors
Deficient
65 = 5 × 13. It has 4 divisors, adding up to 84.
Its divisors, itself excluded, add up to less than the number.
Laid out as dots
It fits as 5 × 13. The more divisors, the closer to a square.
- Prime factors
- 5 × 13
- Divisors
- 1, 5, 13, 65
- Sum of divisors
- 84
- Sum without itself
- 19
- Coprime below it
- 48
- Digit sum
- 11
- Digital root
- 2
- Roman numeral
- LXV
- Binary
- 1000001
- Octal
- 101
- Hexadecimal
- 41
- Base 36
- 1T
- Bits
- 7 bits
- Collatz steps
- 27 steps · peaks at 196
- 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 65 a prime number?
No. It breaks down into 5 × 13.
Q. What are the divisors of 65?
1, 5, 13, 65 — 4 divisors in all, adding up to 84.
Q. How is 65 written in binary?
1000001, which is 7 bits. In hexadecimal it is 41.
Q. How many Collatz steps does 65 take?
It reaches 1 in 27, peaking at 196 on the way.