161
CLXI
10100001
The number 161 — factors and divisors
Deficient
161 = 7 × 23. 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 7 × 23. The more divisors, the closer to a square.
- Prime factors
- 7 × 23
- Divisors
- 1, 7, 23, 161
- Sum of divisors
- 192
- Sum without itself
- 31
- Coprime below it
- 132
- Digit sum
- 8
- Digital root
- 8
- Roman numeral
- CLXI
- Binary
- 10100001
- Octal
- 241
- Hexadecimal
- A1
- Base 36
- 4H
- Bits
- 8 bits
- Collatz steps
- 98 steps · peaks at 9,232
- Prime before
- 157
- Prime after
- 163
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.
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200
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 161 a prime number?
No. It breaks down into 7 × 23.
Q. What are the divisors of 161?
1, 7, 23, 161 — 4 divisors in all, adding up to 192.
Q. How is 161 written in binary?
10100001, which is 8 bits. In hexadecimal it is A1.
Q. How many Collatz steps does 161 take?
It reaches 1 in 98, peaking at 9,232 on the way.