# 261 (number)

 ← 260 261 262 →
Cardinal two hundred sixty-one
Ordinal 261st
(two hundred sixty-first)
Factorization 32× 29
Divisors 1, 3, 9, 29, 87, 261
Greek numeral ΣΞΑ´
Roman numeral CCLXI
Binary 1000001012
Ternary 1002003
Quaternary 100114
Quinary 20215
Senary 11136
Octal 4058
Duodecimal 19912
Vigesimal D120
Base 36 7936

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 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]

## In other fields

261 may refer to...

The years 261 AD or 261 BC.

The steam locomotive Milwaukee Road 261.

Alaska Airlines Flight 261, which crashed in the Pacific Ocean near Anacapa Island on January 31, 2000.

## 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.