1989809 has 4 divisors (see below), whose sum is σ = 1996404. Its totient is φ = 1983216.

The previous prime is 1989803. The next prime is 1989811. The reversal of 1989809 is 9089891.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1081600 + 908209 = 1040^2 + 953^2 .

It is a cyclic number.

It is not a de Polignac number, because 1989809 - 2⁸ = 1989553 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1989809.

It is not an unprimeable number, because it can be changed into a prime (1989803) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2822 + ... + 3455.

It is an arithmetic number, because the mean of its divisors is an integer number (499101).

2^1989809 is an apocalyptic number.

It is an amenable number.

1989809 is a deficient number, since it is larger than the sum of its proper divisors (6595).

1989809 is an equidigital number, since it uses as much as digits as its factorization.

1989809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6594.

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

The square root of 1989809 is about 1410.6058981870. The cubic root of 1989809 is about 125.7777428918. Note that the first 4 decimals are identical.

The spelling of 1989809 in words is "one million, nine hundred eighty-nine thousand, eight hundred nine".