20665664 has 14 divisors (see below), whose sum is σ = 41008554. Its totient is φ = 10332800.

The previous prime is 20665663. The next prime is 20665669. The reversal of 20665664 is 46656602.

It can be written as a sum of positive squares in only one way, i.e., 17707264 + 2958400 = 4208^2 + 1720^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20665663) by changing a digit.

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 as a sum of consecutive naturals, namely, 161387 + ... + 161514.

Almost surely, 2^20665664 is an apocalyptic number.

It is an amenable number.

20665664 is a deficient number, since it is larger than the sum of its proper divisors (20342890).

20665664 is an equidigital number, since it uses as much as digits as its factorization.

20665664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 322913 (or 322903 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 35.

The square root of 20665664 is about 4545.9502856939. The cubic root of 20665664 is about 274.4204389403.

The spelling of 20665664 in words is "twenty million, six hundred sixty-five thousand, six hundred sixty-four".