247 (number)

← 246 247 248 →
← 200 210 220 230 240 250 260 270 280 290 → List of numbers — Integers ← 0 100 200 300 400 500 600 700 800 900 →
Cardinal	two hundred forty-seven
Ordinal	247th (two hundred and forty-seventh)
Factorization	13 × 19
Roman numeral	CCXLVII
Binary	111101112
Ternary	1000113
Quaternary	33134
Quinary	14425
Senary	10516
Octal	3678
Duodecimal	18712
Hexadecimal	F716
Vigesimal	C720
Base 36	6V36

247 (two hundred [and] forty seven) is the natural number following 246 and preceding 248.

In mathematics

247 is:

• a semiprime.
• a brilliant number (the product of two primes with the same number of digits).
• a pentagonal number.
• palindromic in bases 18 (DD₁₈) and 246 (11₂₄₆).
• a Harshad number in bases 10, 14, 19, 20, 27, 39, 40, 58, 77, 79, 115, 118, 229 and 235.
• the smallest number which can be expressed as the difference between two integers that contain together all digits 0-9. i.e. 247 = 50123 - 49876.^[1]

The mathematician and philosopher Alex Bellos suggested in 2014 that a candidate for the lowest uninteresting number would be 247 because it was, at the time, "the lowest number not to have its own page on Wikipedia".^[2]

In other fields

• Sometimes (e.g. when it is used in a URL), 247 is used as an alternative to 24/7, an abbreviation which means "24 hours a day, 7 days a week".
• Approximate number of acres in a square kilometer (1 km² ≈ 247.10538 acres).

References

1. Friedman, Erich. "What's Special About This Number?". stetson.edu. Retrieved 15 April 2016.
2. Bellos, Alex (June 2014). The Grapes of Math: How Life Reflects Numbers and Numbers Reflect Life. illus. The Surreal McCoy (1st Simon & Schuster hardcover ed.). N.Y.: Simon & Schuster. pp. 238 & 319 (quoting p. 319). ISBN 978-1-4516-4009-0.