45 (number)

← 44 45 46 →
← 40 41 42 43 44 45 46 47 48 49 → List of numbers Integers ← 0 10 20 30 40 50 60 70 80 90 →
Cardinal	forty-five
Ordinal	45th (forty-fifth)
Factorization	32 × 5
Divisors	1, 3, 5, 9, 15, 45
Greek numeral	ΜΕ´
Roman numeral	XLV, xlv
Binary	1011012
Ternary	12003
Senary	1136
Octal	558
Duodecimal	3912
Hexadecimal	2D16

45 (forty-five) is the natural number following 44 and preceding 46.

In mathematics

45 as the difference of two nonzero squares (in orange)

45 is a composite number and a Størmer number.

Forty-five is conjectured from Ramsey number ${\displaystyle R(5,5)}$. ^{[1] [2]}

${\displaystyle \phi (45)=\phi (\sigma (45))}$ ^[3]

Forty-five degrees is half of a right angle (90°).

In music

45 rpm gramophone record

• A type of gramophone record classified by its rotational speed of 45 revolutions per minute (rpm)

In other fields

• Guns or ammunition of .45 caliber. In the United States, "45" is often a reference to one of two specific .45 caliber cartridges—the .45 Colt or the .45 ACP.
• In years of marriage, the sapphire wedding anniversary.
• Issue 45 of The North Briton was thought to be seditious but its publisher, John Wilkes, was celebrated as a champion of liberty. The number 45 was used as a symbol of support for him. Banquets were held with a theme of 45 while many items were produced showing the number or featuring it in some way. For example, a wig was produced with 45 curls. ^[4]

References

1. Sloane, N. J. A. (ed.). "SequenceA120414(Conjectured Ramsey number R(n,n).)". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation. Retrieved 2023-02-17.
2. Sloane, N. J. A. (ed.). "SequenceA212954(Triangle read by rows: two color Ramsey numbers)". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation. Retrieved 2022-11-25.
3. Sloane, N. J. A. (ed.). "SequenceA006872". The On-Line Encyclopedia of Integer Sequences . OEIS Foundation.
4. Arthur Hill Cash (2007), John Wilkes: The Scandalous Father of Civil Liberty, Yale University Press, p.  219, ISBN   978-0-300-12363-0