861555072 has 128 divisors (see below), whose sum is σ = 2630327040. Its totient is φ = 244758528.

The previous prime is 861555061. The next prime is 861555143. The reversal of 861555072 is 270555168.

It is a tau number, because it is divible by the number of its divisors (128).

It is a self number, because there is not a number n which added to its sum of digits gives 861555072.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 528723 + ... + 530349.

It is an arithmetic number, because the mean of its divisors is an integer number (20549430).

Almost surely, 2^861555072 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 861555072, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1315163520).

861555072 is an abundant number, since it is smaller than the sum of its proper divisors (1768771968).

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

861555072 is a wasteful number, since it uses less digits than its factorization.

861555072 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1848 (or 1836 counting only the distinct ones).

The product of its (nonzero) digits is 84000, while the sum is 39.

The square root of 861555072 is about 29352.2583798930. The cubic root of 861555072 is about 951.5413839793.

The spelling of 861555072 in words is "eight hundred sixty-one million, five hundred fifty-five thousand, seventy-two".