285 (number)

← 284 285 286 →
← 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 eighty-five
Ordinal	285th (two hundred eighty-fifth)
Factorization	3 × 5 × 19
Divisors	1, 3, 5, 15, 19, 57, 95, 285
Greek numeral	ΣΠΕ´
Roman numeral	CCLXXXV, cclxxxv
Binary	1000111012
Ternary	1011203
Senary	11536
Octal	4358
Duodecimal	1B912
Hexadecimal	11D16

285 is the natural number following 284 and preceding 286.

In mathematics

• 285 is an odd composite number. ^[1]
• 285 is the 9th square pyramidal number. That means it is the sum of a number of consecutive perfect squares starting with 1. For 285, it is the sum of all of the single digits' perfect squares. ^[2]
• 285 is the number of variations possible with a binary rooted tree with 13 points. A binary rooted tree means that it always begins with 1 point that is rooted. From there, each point can branch in up to two directions. ^[3]
• 285 is a sphenic number ^[4] which means that it has three distinct prime factors. ^[5]
• 285 is a Harshad number. That means that it is divisible by the sum of its digits. 285 is divisible by 15. ^[6]
• 285 is a repdigit number in base 7. In base 7, 285 is 555. ^[7]
• 285 is a very symmetric number. If flipped horizontally, these numbers are symmetrical. ^[8]

References

1. "Composite numbers". mathworld.wolfram.com.
2. "Square pyramidal number sequence". marhworld.wolfram.com.
3. "Binary rooted tree". mathworld.wolfram.com.
4. Sloane, N. J. A. (ed.). "SequenceA007304(sphenic numbers)". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
5. "Sphenic numbers". mathworld.wolfram.com.
6. "Harshad numbers". mathworld.wolfram.com.
7. "Repdigit numbers". mathworld.wolfram.com.
8. Sloane, N. J. A. (ed.). "SequenceA053701(Vertically symmetric numbers)". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation.