The Number
21
Twenty-One
In Base 11 Undecimal Is
1a11
The numbers with a 11 subscript use Base 11 Undecimal notation.
For more familiar numbers: See Twenty-One in Base 10 Decimal
Nearby Numbers
Positive, nonzero integers within three units
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.
0.0584210584210583911
The reciprocal of 21 in Base 11 Undecimal.
Palindrome?
A numerical palindrome has the same value when all of its digits are reversed.
The number 1a11 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 11 Undecimal
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 number twenty-one has the following 2 prime factors:
Prime Factorization
The prime factorization of a positive integer is the unique list of prime factors together with their multiplicities
3111
·
7111
= 1a11
Base Conversions
The number twenty-one in 35 different bases