21023131123 has 4 divisors (see below), whose sum is σ = 21024452128. Its totient is φ = 21021810120.

The previous prime is 21023131099. The next prime is 21023131133. The reversal of 21023131123 is 32113132012.

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 21023131123 - 2⁵ = 21023131091 is a prime.

It is a super-2 number, since 2×21023131123² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21023131123.

It is not an unprimeable number, because it can be changed into a prime (21023131133) 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, 636336 + ... + 668557.

It is an arithmetic number, because the mean of its divisors is an integer number (5256113032).

Almost surely, 2^21023131123 is an apocalyptic number.

21023131123 is a deficient number, since it is larger than the sum of its proper divisors (1321005).

21023131123 is a wasteful number, since it uses less digits than its factorization.

21023131123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1321004.

The product of its (nonzero) digits is 216, while the sum is 19.

Adding to 21023131123 its reverse (32113132012), we get a palindrome (53136263135).

The spelling of 21023131123 in words is "twenty-one billion, twenty-three million, one hundred thirty-one thousand, one hundred twenty-three".