21111023 has 4 divisors (see below), whose sum is σ = 21625968. Its totient is φ = 20596080.

The previous prime is 21111007. The next prime is 21111029. The reversal of 21111023 is 32011112.

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 21111023 - 2⁴ = 21111007 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21110995 and 21111013.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21111029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 257411 + ... + 257492.

It is an arithmetic number, because the mean of its divisors is an integer number (5406492).

Almost surely, 2^21111023 is an apocalyptic number.

21111023 is a deficient number, since it is larger than the sum of its proper divisors (514945).

21111023 is an equidigital number, since it uses as much as digits as its factorization.

21111023 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 514944.

The product of its (nonzero) digits is 12, while the sum is 11.

The square root of 21111023 is about 4594.6733289756. The cubic root of 21111023 is about 276.3777602228.

Adding to 21111023 its reverse (32011112), we get a palindrome (53122135).

The spelling of 21111023 in words is "twenty-one million, one hundred eleven thousand, twenty-three".