19995809 has 8 divisors (see below), whose sum is σ = 21963840. Its totient is φ = 18119376.

The previous prime is 19995797. The next prime is 19995851. The reversal of 19995809 is 90859991.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19995809 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (19995869) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 22442 + ... + 23315.

It is an arithmetic number, because the mean of its divisors is an integer number (2745480).

Almost surely, 2^19995809 is an apocalyptic number.

19995809 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

It is an amenable number.

19995809 is a deficient number, since it is larger than the sum of its proper divisors (1968031).

19995809 is a wasteful number, since it uses less digits than its factorization.

19995809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45799.

The product of its (nonzero) digits is 262440, while the sum is 50.

The square root of 19995809 is about 4471.6673624052. The cubic root of 19995809 is about 271.4228001279.

The spelling of 19995809 in words is "nineteen million, nine hundred ninety-five thousand, eight hundred nine".