161 (number)

← 160 161 162 →
← 160 161 162 163 164 165 166 167 168 169 → List of numbers Integers ← 0 100 200 300 400 500 600 700 800 900 →
Cardinal	one hundred sixty-one
Ordinal	161st (one hundred sixty-first)
Factorization	7 × 23
Divisors	1, 7, 23, 161
Greek numeral	ΡΞΑ´
Roman numeral	CLXI, clxi
Binary	101000012
Ternary	122223
Senary	4256
Octal	2418
Duodecimal	11512
Hexadecimal	A116

161 (one hundred [and] sixty-one) is the natural number following 160 and preceding 162.

In mathematics

• 161 is the sum of five consecutive prime numbers: 23, 29, 31, 37, and 41.
• 161 is a hexagonal pyramidal number. ^[1]
• 161 is a semiprime. Since its prime factors 7 and 23 are both Gaussian primes, 161 is a Blum integer.
• 161 is a palindromic number. ^[2]
• ⁠161/72⁠ is a commonly used rational approximation of the square root of 5 and is the closest fraction with denominator <300 to that number.

In other fields

• 161 as a code for Anti-Fascist Action (A=1, F=6, by order of the alphabet), sometimes used in 161>88 ^[3] (88 being code for Heil Hitler among neo-nazis, as H=8)

External links

• Number Facts and Trivia: 161
• The Number 161
• VirtueScience: 161 Archived 2021-01-24 at the Wayback Machine

References

1. "Sloane's A002412 : Hexagonal pyramidal numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-28.
2. "A002113 - Oeis".
3. "161>88". Czech Republic: Antifascist Action. 2012. Archived from the original (Documentary) on 3 January 2018. Retrieved 2 January 2018.