21123232121 has 4 divisors (see below), whose sum is σ = 22234981200. Its totient is φ = 20011483044.

The previous prime is 21123232099. The next prime is 21123232133. The reversal of 21123232121 is 12123232112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21123232121 - 2²² = 21119037817 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21123232093 and 21123232102.

It is not an unprimeable number, because it can be changed into a prime (21123232171) 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 3 ways as a sum of consecutive naturals, for example, 555874511 + ... + 555874548.

It is an arithmetic number, because the mean of its divisors is an integer number (5558745300).

Almost surely, 2^21123232121 is an apocalyptic number.

It is an amenable number.

21123232121 is a deficient number, since it is larger than the sum of its proper divisors (1111749079).

21123232121 is a wasteful number, since it uses less digits than its factorization.

21123232121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1111749078.

The product of its digits is 288, while the sum is 20.

Adding to 21123232121 its reverse (12123232112), we get a palindrome (33246464233).

Subtracting from 21123232121 its reverse (12123232112), we obtain a palindrome (9000000009).

The spelling of 21123232121 in words is "twenty-one billion, one hundred twenty-three million, two hundred thirty-two thousand, one hundred twenty-one".