21123223123 has 4 divisors (see below), whose sum is σ = 21332364048. Its totient is φ = 20914082200.

The previous prime is 21123223073. The next prime is 21123223157. The reversal of 21123223123 is 32132232112.

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 21123223123 - 2⁹ = 21123222611 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21123223094 and 21123223103.

It is not an unprimeable number, because it can be changed into a prime (21123223523) 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, 104570311 + ... + 104570512.

It is an arithmetic number, because the mean of its divisors is an integer number (5333091012).

Almost surely, 2^21123223123 is an apocalyptic number.

21123223123 is a deficient number, since it is larger than the sum of its proper divisors (209140925).

21123223123 is a wasteful number, since it uses less digits than its factorization.

21123223123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 209140924.

The product of its digits is 864, while the sum is 22.

Adding to 21123223123 its reverse (32132232112), we get a palindrome (53255455235).

The spelling of 21123223123 in words is "twenty-one billion, one hundred twenty-three million, two hundred twenty-three thousand, one hundred twenty-three".