247 (number)

From HandWiki
Short description: Natural number
← 246 247 248 →
Cardinaltwo hundred forty-seven
Ordinal247th
(two hundred forty-seventh)
Factorization13 × 19
Greek numeralΣΜΖ´
Roman numeralCCXLVII
Binary111101112
Ternary1000113
Quaternary33134
Quinary14425
Senary10516
Octal3678
Duodecimal18712
HexadecimalF716
VigesimalC720
Base 366V36

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).[1]
  • a pentagonal number.[2]
  • palindromic in base 18 (DD18).
  • 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 the decimal digits 0–9. i.e. 247 = 50123 - 49876.[3]
  • 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".[4][nb 1] The lowest uninteresting number would by itself be interesting.

In other fields

  • Sometimes 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).

Notes

  1. (As of March 2022), this number is 198

References

  1. "Sloane's A078972 : Brilliant numbers". OEIS Foundation. https://oeis.org/A078972. 
  2. "Sloane's A000326 : Pentagonal numbers". OEIS Foundation. https://oeis.org/A000326. 
  3. Friedman, Erich. "What's Special About This Number?". stetson.edu. http://www2.stetson.edu/~efriedma/numbers.html. 
  4. 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.