20904905 has 16 divisors (see below), whose sum is σ = 28882560. Its totient is φ = 14228352.

The previous prime is 20904899. The next prime is 20904931. The reversal of 20904905 is 50940902.

20904905 is nontrivially palindromic in base 8.

It is a cyclic number.

It is not a de Polignac number, because 20904905 - 2⁸ = 20904649 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2717 + ... + 7013.

It is an arithmetic number, because the mean of its divisors is an integer number (1805160).

Almost surely, 2^20904905 is an apocalyptic number.

It is an amenable number.

20904905 is a deficient number, since it is larger than the sum of its proper divisors (7977655).

20904905 is a wasteful number, since it uses less digits than its factorization.

20904905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4448.

The product of its (nonzero) digits is 3240, while the sum is 29.

The square root of 20904905 is about 4572.1882069749. The cubic root of 20904905 is about 275.4753431754.

The spelling of 20904905 in words is "twenty million, nine hundred four thousand, nine hundred five".