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169 (number)

Field	Value
number	169
divisor	1, 13, 169

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. 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". OEIS Foundation.

Info: Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

integers

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