861505866 has 48 divisors (see below), whose sum is σ = 2115990240. Its totient is φ = 251125920.

The previous prime is 861505829. The next prime is 861505877. The reversal of 861505866 is 668505168.

861505866 is a `hidden beast` number, since 8 + 61 + 5 + 0 + 586 + 6 = 666.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 92440 + ... + 101331.

It is an arithmetic number, because the mean of its divisors is an integer number (44083130).

Almost surely, 2^861505866 is an apocalyptic number.

861505866 is an abundant number, since it is smaller than the sum of its proper divisors (1254484374).

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

861505866 is a wasteful number, since it uses less digits than its factorization.

861505866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 193811 (or 193808 counting only the distinct ones).

The product of its (nonzero) digits is 345600, while the sum is 45.

The square root of 861505866 is about 29351.4201700701. The cubic root of 861505866 is about 951.5232685048.

The spelling of 861505866 in words is "eight hundred sixty-one million, five hundred five thousand, eight hundred sixty-six".