819986 has 4 divisors (see below), whose sum is σ = 1229982. Its totient is φ = 409992.

The previous prime is 819977. The next prime is 819989. The reversal of 819986 is 689918.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 689918 = 2 ⋅344959.

It can be written as a sum of positive squares in only one way, i.e., 819025 + 961 = 905^2 + 31^2 .

It is not an unprimeable number, because it can be changed into a prime (819989) by changing a digit.

819986 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 as a sum of consecutive naturals, namely, 204995 + ... + 204998.

2⁸¹⁹⁹⁸⁶ is an apocalyptic number.

819986 is a deficient number, since it is larger than the sum of its proper divisors (409996).

819986 is a wasteful number, since it uses less digits than its factorization.

819986 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 409995.

The product of its digits is 31104, while the sum is 41.

The square root of 819986 is about 905.5307835739. The cubic root of 819986 is about 93.5984835511.

The spelling of 819986 in words is "eight hundred nineteen thousand, nine hundred eighty-six".