121
CXXI
1111001
The number 121 — factors and divisors
Deficient
121 = 11². It has 3 divisors, adding up to 133.
Its divisors, itself excluded, add up to less than the number.
Families it belongs to
Square
A number times itself — the dots lay out as a square.
Laid out as dots
It fits as 11 × 11. The more divisors, the closer to a square.
- Prime factors
- 11²
- Divisors
- 1, 11, 121
- Sum of divisors
- 133
- Sum without itself
- 12
- Coprime below it
- 110
- Digit sum
- 4
- Digital root
- 4
- Roman numeral
- CXXI
- Binary
- 1111001
- Octal
- 171
- Hexadecimal
- 79
- Base 36
- 3D
- Bits
- 7 bits
- Collatz steps
- 95 steps · peaks at 9,232
- Prime before
- 113
- Prime after
- 127
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 121 a prime number?
No. It breaks down into 11².
Q. What are the divisors of 121?
1, 11, 121 — 3 divisors in all, adding up to 133.
Q. How is 121 written in binary?
1111001, which is 7 bits. In hexadecimal it is 79.
Q. How many Collatz steps does 121 take?
It reaches 1 in 95, peaking at 9,232 on the way.