215 (number)

215 (two hundred [and] fifteen) is the natural number following 214 and preceding 216.

← 214 215 216 →
Cardinaltwo hundred fifteen
Ordinal215th
(two hundred fifteenth)
Factorization5 × 43
Divisors5, 43
Greek numeralΣΙΕ´
Roman numeralCCXV
Binary110101112
Ternary212223
Senary5556
Octal3278
Duodecimal15B12
HexadecimalD716

In mathematicsEdit

  • 215 is a composite number and a semiprime.
  •  
  • 215 is the second smallest integer (after 5) such that   is twice a square:  .[1]
  • 215 is a vertically symmetric number on a calculator display (sequence A053701 in the OEIS).
  • There are 215 sequences of four integers, counting re-arrangements as distinct, such that the sum of their reciprocals is 1.[2] These are
    • 24 arrangements of (2,3,7,42), (2,3,8,24), (2,3,9,18), (2,3,10,15), (2,4,5,20) and (2,4,6,12).
    • 12 arrangements of (3,3,4,12), (3,4,4,6), (2,3,12,12), (2,4,8,8) and (2,5,5,10).
    • 6 arrangements of (3,3,6,6).
    • 4 arrangements of (2,6,6,6).
    • 1 arrangement of (4,4,4,4).

In other fieldsEdit

215 is also:

ReferencesEdit

  1. ^ (sequence A144796 in the OEIS)
  2. ^ (sequence A002967 in the OEIS)