70 (number): Wikis

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Encyclopedia

70
Cardinal seventy
Ordinal 70th
(seventieth)
Factorization $2 \cdot 5 \cdot 7$
Divisors 1,2 5, 7, 10, 14, 35, 70
Roman numeral LXX
Binary 10001102
Octal 1068
Duodecimal 5A12
Hebrew ע (Ayin)

70 (seventy) is the natural number following 69 and preceding 71.

In mathematics

Its factorization makes it a sphenic number. 70 is a Pell number and a generalized heptagonal number, one of only two numbers to be both.[1] Also, it is the seventh pentagonal number and the fourth 13-gonal number, as well as the fifth pentatope number. It is the smallest weird number.

Since it is possible to find sequences of 70 consecutive integers such that each inner member member shares a factor with either the first or the last member, 70 is an Erdős–Woods number.

In base 10, it is a Harshad number.

70 is:

Number name

The French do not have a word for 70, instead using "soixante-dix" (60 + 10). Other French-speaking countries such as Belgium and Switzerland do have a word for it, using "septante."[2]

Notes

1. ^ B. Srinivasa Rao, "Heptagonal Numbers in the Pell Sequence and Diophantine Equations $2x^2 = y^2(5y - 3)^2 \pm 2$" Fib. Quart. 43 3: 194
2. ^ Peter Higgins, Number Story. London: Copernicus Books (2008): 19. "Belgian French speakers however grew tired of this and introduced the new names septante, octante, nonante etc. for these numbers."

Simple English

Order ••••• ••••• ••••• ••••• ••••• ••••• ••••• ••••• ••••• ••••• ••••• ••••• ••••• ••••• seventieth

Seventy is the number that is after sixty-nine and before seventy-one.

The prime factors of seventy are 2, 5, and 7. (2 * 5 * 7 = 70)