21021111011 has 4 divisors (see below), whose sum is σ = 21021430632. Its totient is φ = 21020791392.

The previous prime is 21021110989. The next prime is 21021111029. The reversal of 21021111011 is 11011112012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21021111011 - 2¹⁸ = 21020848867 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21021110983 and 21021111001.

It is not an unprimeable number, because it can be changed into a prime (21021111311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20921 + ... + 206106.

It is an arithmetic number, because the mean of its divisors is an integer number (5255357658).

Almost surely, 2^21021111011 is an apocalyptic number.

21021111011 is a deficient number, since it is larger than the sum of its proper divisors (319621).

21021111011 is an equidigital number, since it uses as much as digits as its factorization.

21021111011 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 319620.

The product of its (nonzero) digits is 4, while the sum is 11.

Adding to 21021111011 its reverse (11011112012), we get a palindrome (32032223023).

The spelling of 21021111011 in words is "twenty-one billion, twenty-one million, one hundred eleven thousand, eleven".