231809021 has 4 divisors (see below), whose sum is σ = 231853500. Its totient is φ = 231764544.

The previous prime is 231808981. The next prime is 231809023. The reversal of 231809021 is 120908132.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 96924025 + 134884996 = 9845^2 + 11614^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-231809021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (231809023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13196 + ... + 25253.

It is an arithmetic number, because the mean of its divisors is an integer number (57963375).

Almost surely, 2^231809021 is an apocalyptic number.

It is an amenable number.

231809021 is a deficient number, since it is larger than the sum of its proper divisors (44479).

231809021 is an equidigital number, since it uses as much as digits as its factorization.

231809021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44478.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 231809021 is about 15225.2757282093. The cubic root of 231809021 is about 614.2947131057.

The spelling of 231809021 in words is "two hundred thirty-one million, eight hundred nine thousand, twenty-one".