21620665 has 8 divisors (see below), whose sum is σ = 28303488. Its totient is φ = 15724080.

The previous prime is 21620659. The next prime is 21620693. The reversal of 21620665 is 56602612.

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

It is not a de Polignac number, because 21620665 - 2⁹ = 21620153 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 196497 + ... + 196606.

It is an arithmetic number, because the mean of its divisors is an integer number (3537936).

Almost surely, 2^21620665 is an apocalyptic number.

It is an amenable number.

21620665 is a deficient number, since it is larger than the sum of its proper divisors (6682823).

21620665 is a wasteful number, since it uses less digits than its factorization.

21620665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 393119.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 21620665 is about 4649.8026839856. The cubic root of 21620665 is about 278.5841150730.

The spelling of 21620665 in words is "twenty-one million, six hundred twenty thousand, six hundred sixty-five".