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# 291 (number)

 ← 290 291 292 →
Cardinaltwo hundred ninety-one
Ordinal291st
(two hundred ninety-first)
Factorization3 × 97
Greek numeralΣϞΑ´
Roman numeralCCXCI
Binary1001000112
Ternary1012103
Quaternary102034
Quinary21315
Senary12036
Octal4438
Duodecimal20312
VigesimalEB20
Base 368336

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.