21550566 has 8 divisors (see below), whose sum is σ = 43101144. Its totient is φ = 7183520.

The previous prime is 21550561. The next prime is 21550589. The reversal of 21550566 is 66505512.

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

21550566 is an admirable number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21550561) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1795875 + ... + 1795886.

It is an arithmetic number, because the mean of its divisors is an integer number (5387643).

Almost surely, 2^21550566 is an apocalyptic number.

21550566 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21550566 is a wasteful number, since it uses less digits than its factorization.

21550566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3591766.

The product of its (nonzero) digits is 9000, while the sum is 30.

The square root of 21550566 is about 4642.2587174779. The cubic root of 21550566 is about 278.2827118986.

The spelling of 21550566 in words is "twenty-one million, five hundred fifty thousand, five hundred sixty-six".