21806608 has 20 divisors (see below), whose sum is σ = 43708140. Its totient is φ = 10527104.

The previous prime is 21806593. The next prime is 21806621. The reversal of 21806608 is 80660812.

It can be written as a sum of positive squares in 2 ways, for example, as 10837264 + 10969344 = 3292^2 + 3312^2 .

It is a plaindrome in base 11.

It is a self number, because there is not a number n which added to its sum of digits gives 21806608.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23035 + ... + 23962.

It is an arithmetic number, because the mean of its divisors is an integer number (2185407).

Almost surely, 2^21806608 is an apocalyptic number.

It is an amenable number.

21806608 is an abundant number, since it is smaller than the sum of its proper divisors (21901532).

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

21806608 is a wasteful number, since it uses less digits than its factorization.

21806608 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47034 (or 47028 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 31.

The square root of 21806608 is about 4669.7545974066. The cubic root of 21806608 is about 279.3804669557.

The spelling of 21806608 in words is "twenty-one million, eight hundred six thousand, six hundred eight".