20904691 has 4 divisors (see below), whose sum is σ = 20913984. Its totient is φ = 20895400.

The previous prime is 20904673. The next prime is 20904701. The reversal of 20904691 is 19640902.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 20904691 - 2¹⁵ = 20871923 is a prime.

It is a super-2 number, since 2×20904691² = 874012211610962, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20904641) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1086 + ... + 6556.

It is an arithmetic number, because the mean of its divisors is an integer number (5228496).

Almost surely, 2^20904691 is an apocalyptic number.

20904691 is a deficient number, since it is larger than the sum of its proper divisors (9293).

20904691 is an equidigital number, since it uses as much as digits as its factorization.

20904691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9292.

The product of its (nonzero) digits is 3888, while the sum is 31.

The square root of 20904691 is about 4572.1648045537. The cubic root of 20904691 is about 275.4744031739.

The spelling of 20904691 in words is "twenty million, nine hundred four thousand, six hundred ninety-one".