20256665 has 32 divisors (see below), whose sum is σ = 29296512. Its totient is φ = 13248000.

The previous prime is 20256659. The next prime is 20256689. The reversal of 20256665 is 56665202.

It is not a de Polignac number, because 20256665 - 2¹⁴ = 20240281 is a prime.

It is a Smith number, since the sum of its digits (32) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

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 (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 28970 + ... + 29660.

It is an arithmetic number, because the mean of its divisors is an integer number (915516).

Almost surely, 2^20256665 is an apocalyptic number.

It is an amenable number.

20256665 is a deficient number, since it is larger than the sum of its proper divisors (9039847).

20256665 is a wasteful number, since it uses less digits than its factorization.

20256665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 761.

The product of its (nonzero) digits is 21600, while the sum is 32.

The square root of 20256665 is about 4500.7404946297. The cubic root of 20256665 is about 272.5979896168.

The spelling of 20256665 in words is "twenty million, two hundred fifty-six thousand, six hundred sixty-five".