231420221 has 2 divisors, whose sum is σ = 231420222. Its totient is φ = 231420220.

The previous prime is 231420187. The next prime is 231420223. The reversal of 231420221 is 122024132.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 209844196 + 21576025 = 14486^2 + 4645^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-231420221 is a prime.

Together with 231420223, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 231420221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (231420223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 115710110 + 115710111.

It is an arithmetic number, because the mean of its divisors is an integer number (115710111).

Almost surely, 2^231420221 is an apocalyptic number.

It is an amenable number.

231420221 is a deficient number, since it is larger than the sum of its proper divisors (1).

231420221 is an equidigital number, since it uses as much as digits as its factorization.

231420221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 192, while the sum is 17.

The square root of 231420221 is about 15212.5021281839. The cubic root of 231420221 is about 613.9510804642.

Adding to 231420221 its reverse (122024132), we get a palindrome (353444353).

The spelling of 231420221 in words is "two hundred thirty-one million, four hundred twenty thousand, two hundred twenty-one".