21220566 has 16 divisors (see below), whose sum is σ = 42508800. Its totient is φ = 7062248.

The previous prime is 21220531. The next prime is 21220583. The reversal of 21220566 is 66502212.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 1855 + ... + 6773.

It is an arithmetic number, because the mean of its divisors is an integer number (2656800).

Almost surely, 2^21220566 is an apocalyptic number.

21220566 is an abundant number, since it is smaller than the sum of its proper divisors (21288234).

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

21220566 is a wasteful number, since it uses less digits than its factorization.

21220566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5643.

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 21220566 is about 4606.5785568033. The cubic root of 21220566 is about 276.8549680198.

Adding to 21220566 its reverse (66502212), we get a palindrome (87722778).

The spelling of 21220566 in words is "twenty-one million, two hundred twenty thousand, five hundred sixty-six".