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69 (number)

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Cardinal 69
sixty-nine
Ordinal 69th
sixty-ninth
Numeral system sexagesimal
Factorization [ 3 \cdot 23]
Roman numeral LXIX
Binary 1000101
Duodecimal 59
Hexadecimal 45

69 (sixty-nine) is the natural number following 68 and preceding 70.

In mathematics

Adding up the divisors of 1 through 9 gives 69.

Because 69 has an odd number of 1s in its binary representation, it is sometimes called an "odious number" (see Thue-Morse sequence).

It is the largest number whose factorial is less than 10100 (69! ≈ 1.71x1098). This means it is often the largest factorial that can be calculated by a pocket calculator. (See 449.)

It also has the interesting property of being the only number whose square and cube contain once and only once all numerals from zero to nine when written in decimal notation:

Also, interesting is that 6932 = 6969...

Another interesting property is that 69 is equal to 105 octal, while 105 is equal to 69 hexadecimal. This same property can be applied to all numbers from 64 to 69.

69 is a semiprime.

In astronomy

The Messier object M69 is a magnitude 9.0 globular cluster in the constellation Sagittarius.

In other fields

Sixty-nine is:

 


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