155
CLV
10011011
The number 155 — factors and divisors
Deficient
155 = 5 × 31. It has 4 divisors, adding up to 192.
Its divisors, itself excluded, add up to less than the number.
Laid out as dots
It fits as 5 × 31. The more divisors, the closer to a square.
- Prime factors
- 5 × 31
- Divisors
- 1, 5, 31, 155
- Sum of divisors
- 192
- Sum without itself
- 37
- Coprime below it
- 120
- Digit sum
- 11
- Digital root
- 2
- Roman numeral
- CLV
- Binary
- 10011011
- Octal
- 233
- Hexadecimal
- 9B
- Base 36
- 4B
- Bits
- 8 bits
- Collatz steps
- 85 steps · peaks at 9,232
- Prime before
- 151
- Prime after
- 157
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 155 a prime number?
No. It breaks down into 5 × 31.
Q. What are the divisors of 155?
1, 5, 31, 155 — 4 divisors in all, adding up to 192.
Q. How is 155 written in binary?
10011011, which is 8 bits. In hexadecimal it is 9B.
Q. How many Collatz steps does 155 take?
It reaches 1 in 85, peaking at 9,232 on the way.