21405804 has 24 divisors (see below), whose sum is σ = 57082368. Its totient is φ = 6115920.

The previous prime is 21405803. The next prime is 21405827. The reversal of 21405804 is 40850412.

It is not an unprimeable number, because it can be changed into a prime (21405803) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 127332 + ... + 127499.

It is an arithmetic number, because the mean of its divisors is an integer number (2378432).

Almost surely, 2^21405804 is an apocalyptic number.

It is an amenable number.

21405804 is an abundant number, since it is smaller than the sum of its proper divisors (35676564).

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

21405804 is a wasteful number, since it uses less digits than its factorization.

21405804 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 254845 (or 254843 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 24.

The square root of 21405804 is about 4626.6406819635. The cubic root of 21405804 is about 277.6582070028.

The spelling of 21405804 in words is "twenty-one million, four hundred five thousand, eight hundred four".