68 (number)

← 67 69 → 68
← 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-eight
Ordinal	68th (sixty-eighth)
Factorization	$2^2 \cdot 17$
Divisors	1, 2, 4, 17, 34, 68
Roman numeral	LXVIII
Binary	10001002
Octal	1048
Duodecimal	5812
Hexadecimal	4416

68 (sixty-eight) is the natural number following 67 and preceding 69.

In mathematics

Sixty-eight is a nontotient. It is also a Perrin number, preceded in the sequence by 29, 39, 51 (it is the sum of the first two mentioned). It is also a Happy number.

In normal distribution, 68% of values are within one standard deviation from the mean; see 68-95-99.7 rule.

In science

• The atomic number of erbium, a lanthanide

Astronomy

• Messier object M68, a magnitude 9.0 globular cluster in the constellation Hydra

• The New General Catalogue object NGC 68, a spiral galaxy in the constellation Andromeda

• The Saros number of the solar eclipse series which began on -626 March 16 and ended on 685 August. The duration of Saros series 68 was 1280.1 years, and it contained 72 solar eclipses.

• The Saros number of the lunar eclipse series which began on -613 July 3 and ended on 685 August. The duration of Saros series 68 was 1298.1 years, and it contained 73 lunar eclipses.

In other fields

Sixty-eight is:

• In degrees Fahrenheit, the ideal temperature for developing black-and-white film
• The designation of US Interstate 68, a freeway that runs from West Virginia to Maryland
• The registry of the U.S. Navy's aircraft carrier USS Nimitz (CVN-68), named after Admiral Chester Nimitz
• The number of the French department Haut-Rhin
• A publishing house in Canada for exiled Czech authors, 68 Publishers
• In the restaurant industry, it may can mean "put on order", being the opposite of 86 (number) which means "take away"
• The number of sectors on one cylinder of MFM hard disks with 4 heads and 17 sectors per track
• A reference to the Prague Spring of 1968 in Czechoslovakia
• "Summer '68" is a song by Pink Floyd on the album Atom Heart Mother

Historical years

68 A.D., 68 B.C., 1968, 2068, etc.