21265566 has 32 divisors (see below), whose sum is σ = 50178048. Its totient is φ = 5879520.

The previous prime is 21265553. The next prime is 21265577. The reversal of 21265566 is 66556212.

It is a happy number.

It is a Curzon number.

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 15 ways as a sum of consecutive naturals, for example, 6865 + ... + 9468.

It is an arithmetic number, because the mean of its divisors is an integer number (1568064).

Almost surely, 2^21265566 is an apocalyptic number.

21265566 is an abundant number, since it is smaller than the sum of its proper divisors (28912482).

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

21265566 is a wasteful number, since it uses less digits than its factorization.

21265566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16376.

The product of its digits is 21600, while the sum is 33.

The square root of 21265566 is about 4611.4602893227. The cubic root of 21265566 is about 277.0505279545.

The spelling of 21265566 in words is "twenty-one million, two hundred sixty-five thousand, five hundred sixty-six".