21123212231 has 4 divisors (see below), whose sum is σ = 23043504264. Its totient is φ = 19202920200.

The previous prime is 21123212197. The next prime is 21123212251. The reversal of 21123212231 is 13221232112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21123212231 is a prime.

It is a super-2 number, since 2×21123212231² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21123212251) 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, 960146000 + ... + 960146021.

It is an arithmetic number, because the mean of its divisors is an integer number (5760876066).

Almost surely, 2^21123212231 is an apocalyptic number.

21123212231 is a deficient number, since it is larger than the sum of its proper divisors (1920292033).

21123212231 is a wasteful number, since it uses less digits than its factorization.

21123212231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1920292032.

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

Adding to 21123212231 its reverse (13221232112), we get a palindrome (34344444343).

The spelling of 21123212231 in words is "twenty-one billion, one hundred twenty-three million, two hundred twelve thousand, two hundred thirty-one".