19890905 has 4 divisors (see below), whose sum is σ = 23869092. Its totient is φ = 15912720.

The previous prime is 19890881. The next prime is 19890911. The reversal of 19890905 is 50909891.

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 6370576 + 13520329 = 2524^2 + 3677^2 .

It is not a de Polignac number, because 19890905 - 2⁶ = 19890841 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1989086 + ... + 1989095.

It is an arithmetic number, because the mean of its divisors is an integer number (5967273).

Almost surely, 2^19890905 is an apocalyptic number.

It is an amenable number.

19890905 is a deficient number, since it is larger than the sum of its proper divisors (3978187).

19890905 is an equidigital number, since it uses as much as digits as its factorization.

19890905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3978186.

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

The square root of 19890905 is about 4459.9220845212. The cubic root of 19890905 is about 270.9473125515.

The spelling of 19890905 in words is "nineteen million, eight hundred ninety thousand, nine hundred five".