20705647 has 4 divisors (see below), whose sum is σ = 20989360. Its totient is φ = 20421936.

The previous prime is 20705639. The next prime is 20705651. The reversal of 20705647 is 74650702.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20705647 - 2³ = 20705639 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20705147) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 141747 + ... + 141892.

It is an arithmetic number, because the mean of its divisors is an integer number (5247340).

Almost surely, 2^20705647 is an apocalyptic number.

20705647 is a deficient number, since it is larger than the sum of its proper divisors (283713).

20705647 is an equidigital number, since it uses as much as digits as its factorization.

20705647 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 283712.

The product of its (nonzero) digits is 11760, while the sum is 31.

The square root of 20705647 is about 4550.3458110346. The cubic root of 20705647 is about 274.5973037124.

The spelling of 20705647 in words is "twenty million, seven hundred five thousand, six hundred forty-seven".