19909805 has 32 divisors (see below), whose sum is σ = 26943840. Its totient is φ = 14049280.

The previous prime is 19909793. The next prime is 19909823. The reversal of 19909805 is 50890991.

It can be written as a sum of positive squares in 16 ways, for example, as 1359556 + 18550249 = 1166^2 + 4307^2 .

It is not a de Polignac number, because 19909805 - 2⁶ = 19909741 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (41).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 100967 + ... + 101163.

It is an arithmetic number, because the mean of its divisors is an integer number (841995).

Almost surely, 2^19909805 is an apocalyptic number.

It is an amenable number.

19909805 is a deficient number, since it is larger than the sum of its proper divisors (7034035).

19909805 is a wasteful number, since it uses less digits than its factorization.

19909805 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 289.

The product of its (nonzero) digits is 29160, while the sum is 41.

The square root of 19909805 is about 4462.0404525284. The cubic root of 19909805 is about 271.0331018964.

19909805 divided by its sum of digits (41) gives a triangular number (485605 = T₉₈₅).

The spelling of 19909805 in words is "nineteen million, nine hundred nine thousand, eight hundred five".