819989 has 2 divisors, whose sum is σ = 819990. Its totient is φ = 819988.

The previous prime is 819977. The next prime is 819991. The reversal of 819989 is 989918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 792100 + 27889 = 890^2 + 167^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-819989 is a prime.

Together with 819991, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (819289) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 409994 + 409995.

It is an arithmetic number, because the mean of its divisors is an integer number (409995).

2⁸¹⁹⁹⁸⁹ is an apocalyptic number.

It is an amenable number.

819989 is a deficient number, since it is larger than the sum of its proper divisors (1).

819989 is an equidigital number, since it uses as much as digits as its factorization.

819989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 46656, while the sum is 44.

The square root of 819989 is about 905.5324400594. The cubic root of 819989 is about 93.5985976974.

The spelling of 819989 in words is "eight hundred nineteen thousand, nine hundred eighty-nine".