21621804 has 12 divisors (see below), whose sum is σ = 50450904. Its totient is φ = 7207264.

The previous prime is 21621793. The next prime is 21621823. The reversal of 21621804 is 40812612.

It is a tau number, because it is divible by the number of its divisors (12).

It is a zygodrome in base 11.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 900897 + ... + 900920.

It is an arithmetic number, because the mean of its divisors is an integer number (4204242).

Almost surely, 2^21621804 is an apocalyptic number.

It is an amenable number.

21621804 is an abundant number, since it is smaller than the sum of its proper divisors (28829100).

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

21621804 is a wasteful number, since it uses less digits than its factorization.

21621804 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1801824 (or 1801822 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 21621804 is about 4649.9251606881. The cubic root of 21621804 is about 278.5890070245.

The spelling of 21621804 in words is "twenty-one million, six hundred twenty-one thousand, eight hundred four".