861660 has 36 divisors (see below), whose sum is σ = 2614248. Its totient is φ = 229728.

The previous prime is 861659. The next prime is 861691. The reversal of 861660 is 66168.

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2214 + ... + 2573.

It is an arithmetic number, because the mean of its divisors is an integer number (72618).

2⁸⁶¹⁶⁶⁰ is an apocalyptic number.

It is an amenable number.

861660 is an abundant number, since it is smaller than the sum of its proper divisors (1752588).

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

861660 is a wasteful number, since it uses less digits than its factorization.

861660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4802 (or 4797 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 861660 is about 928.2564300882. The cubic root of 861660 is about 95.1580011528.

It can be divided in two parts, 861 and 660, that added together give a square (1521 = 39²).

The spelling of 861660 in words is "eight hundred sixty-one thousand, six hundred sixty".