861395165820 has 720 divisors, whose sum is σ = 3263629501440. Its totient is φ = 189410586624.

The previous prime is 861395165803. The next prime is 861395165857. The reversal of 861395165820 is 28561593168.

861395165820 is a `hidden beast` number, since 8 + 6 + 1 + 3 + 9 + 51 + 6 + 582 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

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 239 ways as a sum of consecutive naturals, for example, 881673172 + ... + 881674148.

It is an arithmetic number, because the mean of its divisors is an integer number (4532818752).

Almost surely, 2^861395165820 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 861395165820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1631814750720).

861395165820 is an abundant number, since it is smaller than the sum of its proper divisors (2402234335620).

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

861395165820 is a wasteful number, since it uses less digits than its factorization.

861395165820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1424 (or 1406 counting only the distinct ones).

The product of its (nonzero) digits is 3110400, while the sum is 54.

The spelling of 861395165820 in words is "eight hundred sixty-one billion, three hundred ninety-five million, one hundred sixty-five thousand, eight hundred twenty".