861305809 has 32 divisors (see below), whose sum is σ = 1090817280. Its totient is φ = 661969152.

The previous prime is 861305807. The next prime is 861305813. The reversal of 861305809 is 908503168.

It is a happy number.

It is not a de Polignac number, because 861305809 - 2¹ = 861305807 is a prime.

It is not an unprimeable number, because it can be changed into a prime (861305807) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 515227 + ... + 516895.

It is an arithmetic number, because the mean of its divisors is an integer number (34088040).

Almost surely, 2^861305809 is an apocalyptic number.

It is an amenable number.

861305809 is a deficient number, since it is larger than the sum of its proper divisors (229511471).

861305809 is a wasteful number, since it uses less digits than its factorization.

861305809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1849.

The product of its (nonzero) digits is 51840, while the sum is 40.

The square root of 861305809 is about 29348.0120110375. The cubic root of 861305809 is about 951.4496092550.

The spelling of 861305809 in words is "eight hundred sixty-one million, three hundred five thousand, eight hundred nine".