Number

45

Positive
Odd
Composite
2 digits

45 is an odd 2-digit integer and a composite number. It has 6 divisors and a digital root of 9.

Number properties

ParityOddnot divisible by 2

SignPositive

PrimalityComposite

Absolute value45

Digit count2

Digit sum9

Digital root9repeated digit sum

PalindromicNoreads differently backwards

Triangular numberYes, the 9th triangular number

Happy numberNosquared-digit sums reach 1

Harshad numberYesdivisible by its own digit sum

Factors & divisors

Prime factorisation3^2 × 5

Distinct prime factors23, 5

Number of divisors6

Sum of divisors σ(n)78

Aliquot sum33sum of the proper divisors

ClassificationDeficientthe aliquot sum is less than the number

Euler's totient φ(n)24integers below n that share no factor with it

SquarefreeNohas a repeated prime factor

All divisors1, 3, 5, 9, 15, 456 in total

Arithmetic

Previous number44

Next number46

Double90

Half22.5

Square2,025

Cube91,125

Square root6.708203932≈irrational, shown to 9 decimal places

Cube root3.556893304≈

Negation-45

Reciprocal0.0222222222≈

45 factorial119,622,220,865,480,194,561,963,161,495,657,715,064,383,733,760,000,000,000

Representations

Decimal45

Binary1011016 bits

Octal55

Hexadecimal2D

Base 3619

Roman numeralXLV

In wordsforty-five

Ordinalforty-fifth

Scientific notation4.5 × 10^1

Engineering notation45

Nearest landmarks

Next prime47+2

Previous prime43−2

Distance to nearest prime2

Nearest square below36

Nearest square above49

Powers & multiples

45 to the power 22,025

45 to the power 391,125

45 to the power 44,100,625

45 to the power 5184,528,125

First ten multiples45, 90, 135, 180, 225, 270, 315, 360, 405, 450

Powers of twoBetween 2^5 (32) and 2^6 (64)

Divisibility tests

Divisible by 2No, remainder 1

Divisible by 3Yes

Divisible by 4No, remainder 1

Divisible by 5Yes

Divisible by 6No, remainder 3

Divisible by 7No, remainder 3

Divisible by 8No, remainder 5

Divisible by 9Yes

Divisible by 10No, remainder 5

Divisible by 11No, remainder 1

Divisible by 12No, remainder 9

Divisible by 100No, remainder 45

Collatz (3n + 1) trajectory

Steps to reach 116the total stopping time

Highest value reached1363× the starting value

Reaches 1Yesthe Collatz conjecture says every positive integer does, but it is unproven

First steps45 → 136 → 68 → 34 → 17 → 52 → 26 → 13 → 40 → 20 → …

Last steps… → 5 → 16 → 8 → 4 → 2 → 1

As a percentage & fraction

As a percentage4,500%

45% as a decimal0.45

45% of 10045

45% of 1,000450

As a fraction of 10045/100

Read another way

As seconds45 seconds

As bytes45 B

As a 24-bit colour#00002D

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45

Number properties

Factors & divisors

Arithmetic

Representations

Nearest landmarks

Powers & multiples

Divisibility tests

Collatz (3n + 1) trajectory

As a percentage & fraction

Read another way

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Neighbouring numbers

Derived from 45

Nearby primes

Other readings

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