99861 has 4 divisors (see below), whose sum is σ = 133152. Its totient is φ = 66572.

The previous prime is 99859. The next prime is 99871. The reversal of 99861 is 16899.

It is a happy number.

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.

It is a cyclic number.

It is not a de Polignac number, because 99861 - 2¹ = 99859 is a prime.

It is a D-number.

It is a nialpdrome in base 10.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 99861.

It is not an unprimeable number, because it can be changed into a prime (99871) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16641 + ... + 16646.

It is an arithmetic number, because the mean of its divisors is an integer number (33288).

2⁹⁹⁸⁶¹ is an apocalyptic number.

It is an amenable number.

99861 is a deficient number, since it is larger than the sum of its proper divisors (33291).

99861 is a wasteful number, since it uses less digits than its factorization.

99861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33290.

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

The square root of 99861 is about 316.0079112934. The cubic root of 99861 is about 46.3943723357.

It can be divided in two parts, 9 and 9861, that added together give a triangular number (9870 = T₁₄₀).

The spelling of 99861 in words is "ninety-nine thousand, eight hundred sixty-one".