21665633 has 8 divisors (see below), whose sum is σ = 25025760. Its totient is φ = 18537280.

The previous prime is 21665587. The next prime is 21665641. The reversal of 21665633 is 33656612.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21665633 - 2⁶ = 21665569 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21665633.

It is not an unprimeable number, because it can be changed into a prime (21665653) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 57743 + ... + 58116.

It is an arithmetic number, because the mean of its divisors is an integer number (3128220).

Almost surely, 2^21665633 is an apocalyptic number.

It is an amenable number.

21665633 is a deficient number, since it is larger than the sum of its proper divisors (3360127).

21665633 is a wasteful number, since it uses less digits than its factorization.

21665633 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115887.

The product of its digits is 19440, while the sum is 32.

The square root of 21665633 is about 4654.6356463208. The cubic root of 21665633 is about 278.7771201669. Note that the first 3 decimals are identical.

The spelling of 21665633 in words is "twenty-one million, six hundred sixty-five thousand, six hundred thirty-three".