The Number
21991
Twenty-One Thousand Nine Hundred and Ninety-One
In Base 18 Octodecimal Is
3dfd18
The numbers with a 18 subscript use Base 18 Octodecimal notation.
For more familiar numbers: See Twenty-One Thousand Nine Hundred and Ninety-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.
2.1991e4
Reciprocal
A number multiplied with its reciprocal is one.
0.0004dgba57015af5918
The reciprocal of 21991 in Base 18 Octodecimal.
Palindrome?
A numerical palindrome has the same value when all of its digits are reversed.
The number 3dfd18 is not a palindrome.
A Prime Number
A prime number is a positive integer that is divisible only by itself and one.
Twenty-one thousand nine hundred and ninety-one is the 2463rd prime number. See primes in Base 18 Octodecimal
Not A Composite
Composites have more than just these two factors.
Twenty-One Thousand Nine Hundred and Ninety-One is not a composite number because it has exactly two factors: One and Twenty-One Thousand Nine Hundred and Ninety-One
Prime Factors
The number twenty-one thousand nine hundred and ninety-one has the following 1 prime factor:
Prime Factorization
The prime factorization of a positive integer is the unique list of prime factors together with their multiplicities
3dfd181
= 3dfd18
Base Conversions
The number twenty-one thousand nine hundred and ninety-one in 35 different bases