21565634 has 4 divisors (see below), whose sum is σ = 32348454. Its totient is φ = 10782816.

The previous prime is 21565633. The next prime is 21565667. The reversal of 21565634 is 43656512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 11937025 + 9628609 = 3455^2 + 3103^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21565634.

It is not an unprimeable number, because it can be changed into a prime (21565633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5391407 + ... + 5391410.

Almost surely, 2^21565634 is an apocalyptic number.

21565634 is a deficient number, since it is larger than the sum of its proper divisors (10782820).

21565634 is a wasteful number, since it uses less digits than its factorization.

21565634 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10782819.

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

The square root of 21565634 is about 4643.8813507668. The cubic root of 21565634 is about 278.3475545421.

The spelling of 21565634 in words is "twenty-one million, five hundred sixty-five thousand, six hundred thirty-four".