1861831881 has 36 divisors (see below), whose sum is σ = 3369039492. Its totient is φ = 982062144.

The previous prime is 1861831877. The next prime is 1861831889. The reversal of 1861831881 is 1881381681.

1861831881 is a `hidden beast` number, since 18 + 618 + 3 + 18 + 8 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 639280656 + 1222551225 = 25284^2 + 34965^2 .

It is not a de Polignac number, because 1861831881 - 2² = 1861831877 is a prime.

It is a super-2 number, since 2×1861831881² = 6932835906215996322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1861831889) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 156646 + ... + 168111.

Almost surely, 2^1861831881 is an apocalyptic number.

It is an amenable number.

1861831881 is a deficient number, since it is larger than the sum of its proper divisors (1507207611).

1861831881 is a wasteful number, since it uses less digits than its factorization.

1861831881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 324790 (or 324780 counting only the distinct ones).

The product of its digits is 73728, while the sum is 45.

The square root of 1861831881 is about 43148.9499408734. The cubic root of 1861831881 is about 1230.2125529955.

The spelling of 1861831881 in words is "one billion, eight hundred sixty-one million, eight hundred thirty-one thousand, eight hundred eighty-one".