21105605 has 8 divisors (see below), whose sum is σ = 26428032. Its totient is φ = 16150288.

The previous prime is 21105587. The next prime is 21105641. The reversal of 21105605 is 50650112.

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 21105605 - 2²⁰ = 20057029 is a prime.

It is a Duffinian number.

It is a congruent 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, 91649 + ... + 91878.

It is an arithmetic number, because the mean of its divisors is an integer number (3303504).

Almost surely, 2^21105605 is an apocalyptic number.

It is an amenable number.

21105605 is a deficient number, since it is larger than the sum of its proper divisors (5322427).

21105605 is a wasteful number, since it uses less digits than its factorization.

21105605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 183555.

The product of its (nonzero) digits is 300, while the sum is 20.

The square root of 21105605 is about 4594.0836953630. The cubic root of 21105605 is about 276.3541147111.

Adding to 21105605 its reverse (50650112), we get a palindrome (71755717).

The spelling of 21105605 in words is "twenty-one million, one hundred five thousand, six hundred five".