20641664 has 16 divisors (see below), whose sum is σ = 41122320. Its totient is φ = 10320768.

The previous prime is 20641661. The next prime is 20641669. The reversal of 20641664 is 46614602.

It is a tau number, because it is divible by the number of its divisors (16).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20641661) by changing a digit.

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 as a sum of consecutive naturals, namely, 80504 + ... + 80759.

It is an arithmetic number, because the mean of its divisors is an integer number (2570145).

Almost surely, 2^20641664 is an apocalyptic number.

It is an amenable number.

20641664 is a deficient number, since it is larger than the sum of its proper divisors (20480656).

20641664 is an equidigital number, since it uses as much as digits as its factorization.

20641664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 161277 (or 161265 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 29.

The square root of 20641664 is about 4543.3098067378. The cubic root of 20641664 is about 274.3141653688.

The spelling of 20641664 in words is "twenty million, six hundred forty-one thousand, six hundred sixty-four".