231440221 has 2 divisors, whose sum is σ = 231440222. Its totient is φ = 231440220.

The previous prime is 231440219. The next prime is 231440243. The reversal of 231440221 is 122044132.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 192127321 + 39312900 = 13861^2 + 6270^2 .

It is a cyclic number.

It is not a de Polignac number, because 231440221 - 2¹ = 231440219 is a prime.

Together with 231440219, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (231440201) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 115720110 + 115720111.

It is an arithmetic number, because the mean of its divisors is an integer number (115720111).

Almost surely, 2^231440221 is an apocalyptic number.

It is an amenable number.

231440221 is a deficient number, since it is larger than the sum of its proper divisors (1).

231440221 is an equidigital number, since it uses as much as digits as its factorization.

231440221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 384, while the sum is 19.

The square root of 231440221 is about 15213.1594680395. The cubic root of 231440221 is about 613.9687664264.

Adding to 231440221 its reverse (122044132), we get a palindrome (353484353).

The spelling of 231440221 in words is "two hundred thirty-one million, four hundred forty thousand, two hundred twenty-one".