The Number

21

Twenty-One

In Base 13 Tridecimal Is

1813

The numbers with a 13 subscript use Base 13 Tridecimal notation.

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

Nearby Numbers

Positive, nonzero integers within three units

18
1513
Eightteen in Base 13 Tridecimal
19
1613
Nineteen in Base 13 Tridecimal
20
1713
Twenty in Base 13 Tridecimal
22
1913
Twenty-Two in Base 13 Tridecimal
23
1a13
Twenty-Three in Base 13 Tridecimal
24
1b13
Twenty-Four in Base 13 Tridecimal

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.

0.080808080808080713

The reciprocal of 21 in Base 13 Tridecimal.

Palindrome?

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

The number 1813 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 13 Tridecimal

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
313
Three in Base 13 Tridecimal
7
713
Seven in Base 13 Tridecimal

Prime Factorization

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

3131 · 7131 = 1813

Base Conversions

The number twenty-one in 35 different bases