21565266 has 16 divisors (see below), whose sum is σ = 45400800. Its totient is φ = 6810048.

The previous prime is 21565261. The next prime is 21565273. The reversal of 21565266 is 66256512.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21565261) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 94471 + ... + 94698.

It is an arithmetic number, because the mean of its divisors is an integer number (2837550).

Almost surely, 2^21565266 is an apocalyptic number.

21565266 is an abundant number, since it is smaller than the sum of its proper divisors (23835534).

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

21565266 is a wasteful number, since it uses less digits than its factorization.

21565266 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 189193.

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

The square root of 21565266 is about 4643.8417285691. The cubic root of 21565266 is about 278.3459712749.

The spelling of 21565266 in words is "twenty-one million, five hundred sixty-five thousand, two hundred sixty-six".