231561864 has 24 divisors (see below), whose sum is σ = 627146910. Its totient is φ = 77187264.

The previous prime is 231561857. The next prime is 231561871. The reversal of 231561864 is 468165132.

It is a happy number.

231561864 is a `hidden beast` number, since 2 + 31 + 5 + 618 + 6 + 4 = 666.

231561864 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (231561857) and next prime (231561871).

It can be written as a sum of positive squares in only one way, i.e., 222308100 + 9253764 = 14910^2 + 3042^2 .

It is a tau number, because it is divible by the number of its divisors (24).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1607997 + ... + 1608140.

Almost surely, 2^231561864 is an apocalyptic number.

231561864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

231561864 is an abundant number, since it is smaller than the sum of its proper divisors (395585046).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

231561864 is a wasteful number, since it uses less digits than its factorization.

231561864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3216149 (or 3216142 counting only the distinct ones).

The product of its digits is 34560, while the sum is 36.

The square root of 231561864 is about 15217.1568960828. The cubic root of 231561864 is about 614.0763131636.

The spelling of 231561864 in words is "two hundred thirty-one million, five hundred sixty-one thousand, eight hundred sixty-four".