18921904 has 20 divisors (see below), whose sum is σ = 37844800. Its totient is φ = 9155520.

The previous prime is 18921899. The next prime is 18921907. The reversal of 18921904 is 40912981.

18921904 is an admirable number.

It is a self number, because there is not a number n which added to its sum of digits gives 18921904.

It is not an unprimeable number, because it can be changed into a prime (18921907) 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, 18579 + ... + 19570.

It is an arithmetic number, because the mean of its divisors is an integer number (1892240).

Almost surely, 2^18921904 is an apocalyptic number.

It is an amenable number.

18921904 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18921904 is a wasteful number, since it uses less digits than its factorization.

18921904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38188 (or 38182 counting only the distinct ones).

The product of its (nonzero) digits is 5184, while the sum is 34.

The square root of 18921904 is about 4349.9314937134. The cubic root of 18921904 is about 266.4740637016.

The spelling of 18921904 in words is "eighteen million, nine hundred twenty-one thousand, nine hundred four".