21559806 has 12 divisors (see below), whose sum is σ = 46712952. Its totient is φ = 7186596.

The previous prime is 21559801. The next prime is 21559829. The reversal of 21559806 is 60895512.

It is a happy number.

21559806 is a `hidden beast` number, since 21 + 559 + 80 + 6 = 666.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21559801) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 598866 + ... + 598901.

It is an arithmetic number, because the mean of its divisors is an integer number (3892746).

Almost surely, 2^21559806 is an apocalyptic number.

21559806 is an abundant number, since it is smaller than the sum of its proper divisors (25153146).

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

21559806 is a wasteful number, since it uses less digits than its factorization.

21559806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1197775 (or 1197772 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 36.

The square root of 21559806 is about 4643.2538160217. The cubic root of 21559806 is about 278.3224782919.

The spelling of 21559806 in words is "twenty-one million, five hundred fifty-nine thousand, eight hundred six".