1999809 has 20 divisors (see below), whose sum is σ = 3415104. Its totient is φ = 1142424.

The previous prime is 1999799. The next prime is 1999817. The reversal of 1999809 is 9089991.

It is not a de Polignac number, because 1999809 - 2⁷ = 1999681 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1999819) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 1197 + ... + 2330.

2^1999809 is an apocalyptic number.

It is an amenable number.

1999809 is a deficient number, since it is larger than the sum of its proper divisors (1415295).

1999809 is an equidigital number, since it uses as much as digits as its factorization.

1999809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3546 (or 3537 counting only the distinct ones).

The product of its (nonzero) digits is 52488, while the sum is 45.

The square root of 1999809 is about 1414.1460320632. The cubic root of 1999809 is about 125.9880941131.

The spelling of 1999809 in words is "one million, nine hundred ninety-nine thousand, eight hundred nine".