861990 has 32 divisors (see below), whose sum is σ = 2108160. Its totient is φ = 225504.

The previous prime is 861979. The next prime is 861997. The reversal of 861990 is 99168.

It is a happy number.

861990 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (861997) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1527 + ... + 2013.

It is an arithmetic number, because the mean of its divisors is an integer number (65880).

2⁸⁶¹⁹⁹⁰ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 861990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1054080).

861990 is an abundant number, since it is smaller than the sum of its proper divisors (1246170).

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

861990 is a wasteful number, since it uses less digits than its factorization.

861990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 556.

The product of its (nonzero) digits is 3888, while the sum is 33.

The square root of 861990 is about 928.4341656790. The cubic root of 861990 is about 95.1701475262.

The spelling of 861990 in words is "eight hundred sixty-one thousand, nine hundred ninety".