999861 has 4 divisors (see below), whose sum is σ = 1333152. Its totient is φ = 666572.

The previous prime is 999853. The next prime is 999863. The reversal of 999861 is 168999.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 168999 = 3 ⋅56333.

It is a cyclic number.

It is not a de Polignac number, because 999861 - 2³ = 999853 is a prime.

It is a D-number.

999861 is a lucky number.

It is a nialpdrome in base 10.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (999863) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 166641 + ... + 166646.

It is an arithmetic number, because the mean of its divisors is an integer number (333288).

2⁹⁹⁹⁸⁶¹ is an apocalyptic number.

It is an amenable number.

999861 is a deficient number, since it is larger than the sum of its proper divisors (333291).

999861 is a wasteful number, since it uses less digits than its factorization.

999861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333290.

The product of its digits is 34992, while the sum is 42.

The square root of 999861 is about 999.9304975847. The cubic root of 999861 is about 99.9953664520.

The spelling of 999861 in words is "nine hundred ninety-nine thousand, eight hundred sixty-one".