861931881 has 16 divisors (see below), whose sum is σ = 1320969600. Its totient is φ = 554806224.

The previous prime is 861931867. The next prime is 861931883. The reversal of 861931881 is 188139168.

It is not a de Polignac number, because 861931881 - 2¹⁴ = 861915497 is a prime.

It is a super-2 number, since 2×861931881² = 1485853134968396322, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (861931883) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 549621 + ... + 551186.

It is an arithmetic number, because the mean of its divisors is an integer number (82560600).

Almost surely, 2^861931881 is an apocalyptic number.

It is an amenable number.

861931881 is a deficient number, since it is larger than the sum of its proper divisors (459037719).

861931881 is a wasteful number, since it uses less digits than its factorization.

861931881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1100845 (or 1100839 counting only the distinct ones).

The product of its digits is 82944, while the sum is 45.

The square root of 861931881 is about 29358.6764177134. The cubic root of 861931881 is about 951.6800855396.

The spelling of 861931881 in words is "eight hundred sixty-one million, nine hundred thirty-one thousand, eight hundred eighty-one".