169 (number)

← 168 169 170 →
← 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-nine
Ordinal	169th; (one hundred sixty-ninth)
Factorization	132
Divisors	1, 13, 169
Greek numeral	ΡΞΘ´
Roman numeral	CLXIX, clxix
Binary	101010012
Ternary	200213
Senary	4416
Octal	2518
Duodecimal	12112
Hexadecimal	A916

169 (one hundred [and] sixty-nine) is the natural number following 168 and preceding 170.

In mathematics

169 is an odd number, a composite number, and a deficient number.

169 is a square number: 13 × 13 = 169, and if each number is reversed the equation is still true: 31 × 31 = 961. 144 shares this property: 12 × 12 = 144, 21 × 21 = 441.

169 is one of the few squares to also be a centered hexagonal number.^[1] Like all odd squares, it is a centered octagonal number. 169 is an odd-indexed Pell number, thus it is also a Markov number, appearing in the solutions (2, 169, 985), (2, 29, 169), (29, 169, 14701), etc. 169 is the sum of seven consecutive primes: 13 + 17 + 19 + 23 + 29 + 31 + 37. 169 is a difference in consecutive cubes, equaling $8^{3}-7^{3}.$

In other fields

169 is known in the computing world as the first number of an automatic IPv4 address assigned by TCP/IP when no external networking device is contactable

References

^ "Sloane's A003215 : Hex (or centered hexagonal) numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-28.

External links

[1] "Sloane's A003215 : Hex (or centered hexagonal) numbers". The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. Retrieved 2016-05-28.

[1]