21012012123 has 16 divisors (see below), whose sum is σ = 28393274880. Its totient is φ = 13819661856.

The previous prime is 21012012083. The next prime is 21012012137. The reversal of 21012012123 is 32121021012.

It is a de Polignac number, because none of the positive numbers 2^k-21012012123 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21012012173) 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 15 ways as a sum of consecutive naturals, for example, 267936 + ... + 337362.

It is an arithmetic number, because the mean of its divisors is an integer number (1774579680).

Almost surely, 2^21012012123 is an apocalyptic number.

21012012123 is a deficient number, since it is larger than the sum of its proper divisors (7381262757).

21012012123 is a wasteful number, since it uses less digits than its factorization.

21012012123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70786.

The product of its (nonzero) digits is 48, while the sum is 15.

Adding to 21012012123 its reverse (32121021012), we get a palindrome (53133033135).

The spelling of 21012012123 in words is "twenty-one billion, twelve million, twelve thousand, one hundred twenty-three".