861665850 has 72 divisors (see below), whose sum is σ = 2400783840. Its totient is φ = 229774320.

The previous prime is 861665807. The next prime is 861665851. The reversal of 861665850 is 58566168.

861665850 is a `hidden beast` number, since 8 + 6 + 1 + 66 + 585 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a junction number, because it is equal to n+sod(n) for n = 861665796 and 861665805.

It is not an unprimeable number, because it can be changed into a prime (861665851) 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 35 ways as a sum of consecutive naturals, for example, 23310 + ... + 47609.

It is an arithmetic number, because the mean of its divisors is an integer number (33344220).

Almost surely, 2^861665850 is an apocalyptic number.

861665850 is an abundant number, since it is smaller than the sum of its proper divisors (1539117990).

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

861665850 is a wasteful number, since it uses less digits than its factorization.

861665850 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70946 (or 70929 counting only the distinct ones).

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

The square root of 861665850 is about 29354.1453631340. The cubic root of 861665850 is about 951.5821650186.

The spelling of 861665850 in words is "eight hundred sixty-one million, six hundred sixty-five thousand, eight hundred fifty".