The Number

21

Twenty-One

In Base 18 Octodecimal Is

1318

The numbers with a 18 subscript use Base 18 Octodecimal notation.

For more familiar numbers: See Twenty-One in Base 10 Decimal

Nearby Numbers

Positive, nonzero integers within three units

18
1018
Eightteen in Base 18 Octodecimal
19
1118
Nineteen in Base 18 Octodecimal
20
1218
Twenty in Base 18 Octodecimal
22
1418
Twenty-Two in Base 18 Octodecimal
23
1518
Twenty-Three in Base 18 Octodecimal
24
1618
Twenty-Four in Base 18 Octodecimal

Scientific Notation

Scientific notation expresses a quantity as the product of its significand with 10 raised to an integer exponent.

2.1e1

Reciprocal

A number multiplied with its reciprocal is one.

0.0f7cf7cf7cf7ce18

The reciprocal of 21 in Base 18 Octodecimal.

Palindrome?

A numerical palindrome has the same value when all of its digits are reversed.

The number 1318 is not a palindrome.

Not A Prime Number

A prime number is a positive integer that is divisible only by itself and one.

Twenty-one is a composite number with 4 total factors (including 1 and itself).   See primes in Base 18 Octodecimal

A Composite

Composites have more than just these two factors.

Twenty-one is a composite number with 4 total factors (including 1 and itself).

Prime Factors

The prime factors of a positive integer are the integers that divide it exactly and are also prime.

The number twenty-one has the following 2 prime factors:

3
318
Three in Base 18 Octodecimal
7
718
Seven in Base 18 Octodecimal

Prime Factorization

The prime factorization of a positive integer is the unique list of prime factors together with their multiplicities

3181 · 7181 = 1318

Base Conversions

The number twenty-one in 35 different bases