231891809 has 2 divisors, whose sum is σ = 231891810. Its totient is φ = 231891808.

The previous prime is 231891799. The next prime is 231891833. The reversal of 231891809 is 908198132.

231891809 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 200307409 + 31584400 = 14153^2 + 5620^2 .

It is a cyclic number.

It is not a de Polignac number, because 231891809 - 2⁸ = 231891553 is a prime.

It is a super-2 number, since 2×231891809² = 107547622162584962, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (231891899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 115945904 + 115945905.

It is an arithmetic number, because the mean of its divisors is an integer number (115945905).

Almost surely, 2^231891809 is an apocalyptic number.

It is an amenable number.

231891809 is a deficient number, since it is larger than the sum of its proper divisors (1).

231891809 is an equidigital number, since it uses as much as digits as its factorization.

231891809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 41.

The square root of 231891809 is about 15227.9942540047. The cubic root of 231891809 is about 614.3678338978.

The spelling of 231891809 in words is "two hundred thirty-one million, eight hundred ninety-one thousand, eight hundred nine".