231212221 has 4 divisors (see below), whose sum is σ = 231390432. Its totient is φ = 231034012.

The previous prime is 231212213. The next prime is 231212231. The reversal of 231212221 is 122212132.

It is a happy number.

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 231212221 - 2³ = 231212213 is a prime.

It is a super-2 number, since 2×231212221² = 106918182279505682, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 231212195 and 231212204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (231212231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 87145 + ... + 89758.

It is an arithmetic number, because the mean of its divisors is an integer number (57847608).

Almost surely, 2^231212221 is an apocalyptic number.

It is an amenable number.

231212221 is a deficient number, since it is larger than the sum of its proper divisors (178211).

231212221 is a wasteful number, since it uses less digits than its factorization.

231212221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 178210.

The product of its digits is 96, while the sum is 16.

The square root of 231212221 is about 15205.6641091404. The cubic root of 231212221 is about 613.7670860222.

Adding to 231212221 its reverse (122212132), we get a palindrome (353424353).

The spelling of 231212221 in words is "two hundred thirty-one million, two hundred twelve thousand, two hundred twenty-one".