861985 has 8 divisors (see below), whose sum is σ = 1095336. Its totient is φ = 648960.

The previous prime is 861979. The next prime is 861997. The reversal of 861985 is 589168.

861985 = 656² + 657².

It can be written as a sum of positive squares in 4 ways, for example, as 73441 + 788544 = 271^2 + 888^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 861985 - 2³ = 861977 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4986 + ... + 5155.

It is an arithmetic number, because the mean of its divisors is an integer number (136917).

2⁸⁶¹⁹⁸⁵ is an apocalyptic number.

861985 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

861985 is the 657-th centered square number.

It is an amenable number.

861985 is a deficient number, since it is larger than the sum of its proper divisors (233351).

861985 is a wasteful number, since it uses less digits than its factorization.

861985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10163.

The product of its digits is 17280, while the sum is 37.

The square root of 861985 is about 928.4314729693. The cubic root of 861985 is about 95.1699635134.

The spelling of 861985 in words is "eight hundred sixty-one thousand, nine hundred eighty-five".