# 291 (number)

 ← 290 291 292 →
Cardinal two hundred ninety-one
Ordinal 291st
(two hundred ninety-first)
Factorization 3 × 97
Greek numeral ΣϞΑ´
Roman numeral CCXCI
Binary 1001000112
Ternary 1012103
Quaternary 102034
Quinary 21315
Senary 12036
Octal 4438
Duodecimal 20312
Vigesimal EB20
Base 36 8336

291 (two hundred [and] ninety one) is the natural number following 290 and preceding 292.

## In mathematics

This number is the product of four divisors: 1, 3, 97 and 291, the sum of its proper divisors (its aliquot sum) is less than 291, making it a deficient number.

Being the product of two prime numbers, 3 and 97, it is a semiprime.

It is part of five Pythagorean triples: (195, 216, 291), (291, 388, 485), (291, 4700, 4709), (291, 14112, 14115), (291, 42340, 42341).

It is a palindrome in base 9: 353.

It is a happy number.

It is the 159th congruent number[1].

It is the sum of the 52nd prime number, 239, and 52, making it part of the ${\displaystyle a(n)=n^{\text{th}}{\text{ prime}}+n}$ series.[2]

## In other fields

291 was the name of a New York City-based arts and literature magazine from 1915 to 1916, the name of which was inspired off the name of an art gallery owned by its publisher. Both names come from the gallery's address at 291 Fifth Avenue.

291 Alice is a main belt asteroid discovered in 1890.

## References

1. ^ "A003273 - OEIS". oeis.org.
2. ^ "A014688 - OEIS". oeis.org.