231309821 has 2 divisors, whose sum is σ = 231309822. Its totient is φ = 231309820.

The previous prime is 231309811. The next prime is 231309833. The reversal of 231309821 is 128903132.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 184660921 + 46648900 = 13589^2 + 6830^2 .

It is a cyclic number.

It is not a de Polignac number, because 231309821 - 2¹⁰ = 231308797 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (231309811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 115654910 + 115654911.

It is an arithmetic number, because the mean of its divisors is an integer number (115654911).

Almost surely, 2^231309821 is an apocalyptic number.

It is an amenable number.

231309821 is a deficient number, since it is larger than the sum of its proper divisors (1).

231309821 is an equidigital number, since it uses as much as digits as its factorization.

231309821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 231309821 is about 15208.8731009237. The cubic root of 231309821 is about 613.8534356111.

The spelling of 231309821 in words is "two hundred thirty-one million, three hundred nine thousand, eight hundred twenty-one".