21039605 has 8 divisors (see below), whose sum is σ = 25380864. Its totient is φ = 16742800.

The previous prime is 21039589. The next prime is 21039611. The reversal of 21039605 is 50693012.

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

It is not a de Polignac number, because 21039605 - 2⁴ = 21039589 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10061 + ... + 11970.

It is an arithmetic number, because the mean of its divisors is an integer number (3172608).

Almost surely, 2^21039605 is an apocalyptic number.

It is an amenable number.

21039605 is a deficient number, since it is larger than the sum of its proper divisors (4341259).

21039605 is a wasteful number, since it uses less digits than its factorization.

21039605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22227.

The product of its (nonzero) digits is 1620, while the sum is 26.

The square root of 21039605 is about 4586.8949192237. The cubic root of 21039605 is about 276.0657487063.

The spelling of 21039605 in words is "twenty-one million, thirty-nine thousand, six hundred five".