231311221 has 4 divisors (see below), whose sum is σ = 239287500. Its totient is φ = 223334944.

The previous prime is 231311219. The next prime is 231311251. The reversal of 231311221 is 122113132.

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

It can be written as a sum of positive squares in 2 ways, for example, as 49196196 + 182115025 = 7014^2 + 13495^2 .

It is a cyclic number.

It is not a de Polignac number, because 231311221 - 2¹ = 231311219 is a prime.

It is a super-3 number, since 3×231311221³ (a number of 26 digits) contains 333 as substring.

It is a Duffinian number.

It is a nialpdrome in base 16.

It is a junction number, because it is equal to n+sod(n) for n = 231311195 and 231311204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (231311251) 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, 3988096 + ... + 3988153.

It is an arithmetic number, because the mean of its divisors is an integer number (59821875).

Almost surely, 2^231311221 is an apocalyptic number.

It is an amenable number.

231311221 is a deficient number, since it is larger than the sum of its proper divisors (7976279).

231311221 is an equidigital number, since it uses as much as digits as its factorization.

231311221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7976278.

The product of its digits is 72, while the sum is 16.

The square root of 231311221 is about 15208.9191266178. The cubic root of 231311221 is about 613.8546740555.

Adding to 231311221 its reverse (122113132), we get a palindrome (353424353).

The spelling of 231311221 in words is "two hundred thirty-one million, three hundred eleven thousand, two hundred twenty-one".