21804557 has 8 divisors (see below), whose sum is σ = 23265792. Its totient is φ = 20363200.

The previous prime is 21804539. The next prime is 21804623. The reversal of 21804557 is 75540812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21804557 - 2⁶ = 21804493 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21804857) 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, 2669 + ... + 7122.

It is an arithmetic number, because the mean of its divisors is an integer number (2908224).

Almost surely, 2^21804557 is an apocalyptic number.

It is an amenable number.

21804557 is a deficient number, since it is larger than the sum of its proper divisors (1461235).

21804557 is a wasteful number, since it uses less digits than its factorization.

21804557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9939.

The product of its (nonzero) digits is 11200, while the sum is 32.

The square root of 21804557 is about 4669.5349875550. The cubic root of 21804557 is about 279.3717077255.

The spelling of 21804557 in words is "twenty-one million, eight hundred four thousand, five hundred fifty-seven".