231221 has 4 divisors (see below), whose sum is σ = 235200. Its totient is φ = 227244.

The previous prime is 231197. The next prime is 231223. The reversal of 231221 is 122132.

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 a de Polignac number, because none of the positive numbers 2^k-231221 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (231223) 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, 1901 + ... + 2018.

It is an arithmetic number, because the mean of its divisors is an integer number (58800).

2²³¹²²¹ is an apocalyptic number.

It is an amenable number.

231221 is a deficient number, since it is larger than the sum of its proper divisors (3979).

231221 is an equidigital number, since it uses as much as digits as its factorization.

231221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3978.

The product of its digits is 24, while the sum is 11.

The square root of 231221 is about 480.8544478322. The cubic root of 231221 is about 61.3774854056.

Adding to 231221 its reverse (122132), we get a palindrome (353353).

The spelling of 231221 in words is "two hundred thirty-one thousand, two hundred twenty-one".