69 (number)

This article is about the number 69. For other uses, see 69 (disambiguation).

← 68 70 → 69
← 60 61 62 63 64 65 66 67 68 69 → List of numbers — Integers 0 10 20 30 40 50 60 70 80 90 →
Cardinal	sixty-nine
Ordinal	69th (sixty-ninth)
Factorization	$3 \cdot 23$
Divisors	1, 3, 23, 69
Roman numeral	LXIX
Binary	10001012
Octal	1058
Duodecimal	5912
Hexadecimal	4516

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

In mathematics

The aliquot sum of sixty-nine is 27 within the aliquot sequence (69,27,13,1,0) 69 being the third composite number in the 13-aliquot tree.

69 is a semiprime. Furthermore, since the two factors of 69 are both Gaussian primes, 69 is a Blum integer.

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." Of note is that 69² (4 761) and 69³ (328 509) together use every decimal digit from 0-9. 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.

On many handheld scientific and graphing calculators, the highest factorial that can be calculated, due to memory limitations, is 69 or 1.711224524×10⁹⁸.

The number 69 written in Western Arabic numeral notation can be rotated 180° and remain visually the same.

In science

• The atomic number of thulium, a lanthanide

Astronomy

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

In other fields

Sixty-nine may also refer to:

• The registry of the U.S. Navy's aircraft carrier USS Dwight D. Eisenhower (CVN-69), named after Dwight D. Eisenhower, the 34th President of the United States and five-star general in the United States Army
• The number of the French department Rhône
• The Taijitu