231439981 has 4 divisors (see below), whose sum is σ = 239420700. Its totient is φ = 223459264.

The previous prime is 231439973. The next prime is 231439987. The reversal of 231439981 is 189934132.

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 199063881 + 32376100 = 14109^2 + 5690^2 .

It is a cyclic number.

It is not a de Polignac number, because 231439981 - 2³ = 231439973 is a prime.

It is a super-2 number, since 2×231439981² = 107128929610560722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (231439987) 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, 3990316 + ... + 3990373.

It is an arithmetic number, because the mean of its divisors is an integer number (59855175).

Almost surely, 2^231439981 is an apocalyptic number.

It is an amenable number.

231439981 is a deficient number, since it is larger than the sum of its proper divisors (7980719).

231439981 is an equidigital number, since it uses as much as digits as its factorization.

231439981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7980718.

The product of its digits is 46656, while the sum is 40.

The square root of 231439981 is about 15213.1515801296. The cubic root of 231439981 is about 613.9685542009.

It can be divided in two parts, 23143 and 9981, that added together give a square (33124 = 182²).

The spelling of 231439981 in words is "two hundred thirty-one million, four hundred thirty-nine thousand, nine hundred eighty-one".