21647705 has 16 divisors (see below), whose sum is σ = 26858304. Its totient is φ = 16739520.

The previous prime is 21647693. The next prime is 21647729. The reversal of 21647705 is 50774612.

It is not a de Polignac number, because 21647705 - 2¹⁴ = 21631321 is a prime.

It is a Duffinian number.

It is a Curzon 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 15 ways as a sum of consecutive naturals, for example, 22535 + ... + 23475.

It is an arithmetic number, because the mean of its divisors is an integer number (1678644).

Almost surely, 2^21647705 is an apocalyptic number.

It is an amenable number.

21647705 is a deficient number, since it is larger than the sum of its proper divisors (5210599).

21647705 is a wasteful number, since it uses less digits than its factorization.

21647705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1096.

The product of its (nonzero) digits is 11760, while the sum is 32.

The square root of 21647705 is about 4652.7094257003. The cubic root of 21647705 is about 278.7002042603.

The spelling of 21647705 in words is "twenty-one million, six hundred forty-seven thousand, seven hundred five".