42
XLII
101010
The number 42 — factors and divisors
Abundant
42 = 2 × 3 × 7. It has 8 divisors, adding up to 96.
Its divisors, itself excluded, add up to more than the number.
Laid out as dots
It fits as 6 × 7. The more divisors, the closer to a square.
- Prime factors
- 2 × 3 × 7
- Divisors
- 1, 2, 3, 6, 7, 14, 21, 42
- Sum of divisors
- 96
- Sum without itself
- 54
- Coprime below it
- 12
- Digit sum
- 6
- Digital root
- 6
- Roman numeral
- XLII
- Binary
- 101010
- Octal
- 52
- Hexadecimal
- 2A
- Base 36
- 16
- Bits
- 6 bits
- Collatz steps
- 8 steps · peaks at 64
- Prime before
- 41
- Prime after
- 43
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 42 a prime number?
No. It breaks down into 2 × 3 × 7.
Q. What are the divisors of 42?
1, 2, 3, 6, 7, 14, 21, 42 — 8 divisors in all, adding up to 96.
Q. How is 42 written in binary?
101010, which is 6 bits. In hexadecimal it is 2A.
Q. How many Collatz steps does 42 take?
It reaches 1 in 8, peaking at 64 on the way.