# 261 (number)

 ← 260 261 262 →
Cardinaltwo hundred sixty-one
Ordinal261st
(two hundred sixty-first)
Factorization32 × 29
Divisors1, 3, 9, 29, 87, 261
Greek numeralΣΞΑ´
Roman numeralCCLXI
Binary1000001012
Ternary1002003
Quaternary100114
Quinary20215
Senary11136
Octal4058
Duodecimal19912
VigesimalD120
Base 367936

261 (two hundred [and] sixty-one) is a natural number proceeded by the number 260 and followed by 262. It has the prime factorization 32·29.

## Mathematical properties

There are six divisors of this number, the divisors being 1, 3, 9, 29, 87, and 261 itself.[1] 261 is a deficient number, since 1 + 3 + 9 + 29 + 87 = 129 < 261.

261 is nonagonal number, Harshad number, unique period in base 2, and the number of possible unfolded tesseract patterns.

261 is a lucky number, as well as an odious number, meaning it has an odd number of 1's in its binary expansion, which is 1000001012 (with 3 ones in it).[2]

261 was once the lowest number not to have its own Wikipedia page, this making it a candidate for the lowest uninteresting Number according to the definition given by Alex Bellos.[3] As of September 2018, the smallest natural number without its own Wikipedia page is 262, and the smallest prime number without its own Wikipedia page is 283.

## In other fields

261 may refer to...

## References

1. ^ "Facts about the number 261". Numbermatics - the number explorer. Retrieved 2017-03-20.
2. ^ "Number Gossip: 261". www.numbergossip.com. Retrieved 2017-03-20.
3. ^ Bellos, Alex (June 2014). The Grapes of Math: How Life Reflects Numbers and Numbers Reflect Life. illus. The Surreal McCoy (1st Simon & Schuster hardcover ed.). N.Y.: Simon & Schuster. pp. 238 & 319 (quoting p. 319). ISBN 978-1-4516-4009-0.