21666522 has 16 divisors (see below), whose sum is σ = 43449120. Its totient is φ = 7202832.

The previous prime is 21666493. The next prime is 21666553. The reversal of 21666522 is 22566612.

It is a self number, because there is not a number n which added to its sum of digits gives 21666522.

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, 2308 + ... + 6975.

It is an arithmetic number, because the mean of its divisors is an integer number (2715570).

Almost surely, 2^21666522 is an apocalyptic number.

21666522 is an abundant number, since it is smaller than the sum of its proper divisors (21782598).

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

21666522 is a wasteful number, since it uses less digits than its factorization.

21666522 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9677.

The product of its digits is 8640, while the sum is 30.

The square root of 21666522 is about 4654.7311415376. The cubic root of 21666522 is about 278.7809331099.

The spelling of 21666522 in words is "twenty-one million, six hundred sixty-six thousand, five hundred twenty-two".