231312021221 has 4 divisors (see below), whose sum is σ = 231356758944. Its totient is φ = 231267283500.

The previous prime is 231312021217. The next prime is 231312021257. The reversal of 231312021221 is 122120213132.

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 231312021221 - 2² = 231312021217 is a prime.

It is a super-2 number, since 2×231312021221² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 231312021193 and 231312021202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (231312024221) 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, 22361105 + ... + 22371446.

It is an arithmetic number, because the mean of its divisors is an integer number (57839189736).

Almost surely, 2^231312021221 is an apocalyptic number.

It is an amenable number.

231312021221 is a deficient number, since it is larger than the sum of its proper divisors (44737723).

231312021221 is an equidigital number, since it uses as much as digits as its factorization.

231312021221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44737722.

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

Adding to 231312021221 its reverse (122120213132), we get a palindrome (353432234353).

The spelling of 231312021221 in words is "two hundred thirty-one billion, three hundred twelve million, twenty-one thousand, two hundred twenty-one".