21011112123 has 4 divisors (see below), whose sum is σ = 28014816168. Its totient is φ = 14007408080.

The previous prime is 21011112097. The next prime is 21011112131. The reversal of 21011112123 is 32121111012.

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 21011112123 - 2¹⁴ = 21011095739 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21011112223) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3501852018 + ... + 3501852023.

It is an arithmetic number, because the mean of its divisors is an integer number (7003704042).

Almost surely, 2^21011112123 is an apocalyptic number.

21011112123 is a deficient number, since it is larger than the sum of its proper divisors (7003704045).

21011112123 is an equidigital number, since it uses as much as digits as its factorization.

21011112123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7003704044.

The product of its (nonzero) digits is 24, while the sum is 15.

Adding to 21011112123 its reverse (32121111012), we get a palindrome (53132223135).

The spelling of 21011112123 in words is "twenty-one billion, eleven million, one hundred twelve thousand, one hundred twenty-three".