21123031111 has 16 divisors (see below), whose sum is σ = 27127908864. Its totient is φ = 15986085984.

The previous prime is 21123031109. The next prime is 21123031123. The reversal of 21123031111 is 11113032112.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21123031111 - 2¹ = 21123031109 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21123032111) 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 15 ways as a sum of consecutive naturals, for example, 5044021 + ... + 5048206.

It is an arithmetic number, because the mean of its divisors is an integer number (1695494304).

Almost surely, 2^21123031111 is an apocalyptic number.

21123031111 is a deficient number, since it is larger than the sum of its proper divisors (6004877753).

21123031111 is a wasteful number, since it uses less digits than its factorization.

21123031111 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10092270.

The product of its (nonzero) digits is 36, while the sum is 16.

Adding to 21123031111 its reverse (11113032112), we get a palindrome (32236063223).

The spelling of 21123031111 in words is "twenty-one billion, one hundred twenty-three million, thirty-one thousand, one hundred eleven".