21665534 has 12 divisors (see below), whose sum is σ = 35721672. Its totient is φ = 9847860.

The previous prime is 21665521. The next prime is 21665551. The reversal of 21665534 is 43556612.

It is a self number, because there is not a number n which added to its sum of digits gives 21665534.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 44522 + ... + 45005.

It is an arithmetic number, because the mean of its divisors is an integer number (2976806).

Almost surely, 2^21665534 is an apocalyptic number.

21665534 is a deficient number, since it is larger than the sum of its proper divisors (14056138).

21665534 is a wasteful number, since it uses less digits than its factorization.

21665534 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89551 (or 89540 counting only the distinct ones).

The product of its digits is 21600, while the sum is 32.

The square root of 21665534 is about 4654.6250117491. The cubic root of 21665534 is about 278.7766955470.

The spelling of 21665534 in words is "twenty-one million, six hundred sixty-five thousand, five hundred thirty-four".