21100000021 has 8 divisors (see below), whose sum is σ = 21460037760. Its totient is φ = 20740042752.

The previous prime is 21100000001. The next prime is 21100000057. The reversal of 21100000021 is 12000000112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21100000021 - 2²⁷ = 20965782293 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21100000001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 772036 + ... + 798898.

It is an arithmetic number, because the mean of its divisors is an integer number (2682504720).

Almost surely, 2^21100000021 is an apocalyptic number.

It is an amenable number.

21100000021 is a deficient number, since it is larger than the sum of its proper divisors (360037739).

21100000021 is a wasteful number, since it uses less digits than its factorization.

21100000021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40235.

The product of its (nonzero) digits is 4, while the sum is 7.

Adding to 21100000021 its reverse (12000000112), we get a palindrome (33100000133).

Subtracting from 21100000021 its reverse (12000000112), we obtain a palindrome (9099999909).

The spelling of 21100000021 in words is "twenty-one billion, one hundred million, twenty-one", and thus it is an aban number.