20509664 has 96 divisors (see below), whose sum is σ = 49996800. Its totient is φ = 8087040.

The previous prime is 20509663. The next prime is 20509679. The reversal of 20509664 is 46690502.

It is a Harshad number since it is a multiple of its sum of digits (32).

It is a self number, because there is not a number n which added to its sum of digits gives 20509664.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20509661) 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 in 15 ways as a sum of consecutive naturals, for example, 259577 + ... + 259655.

It is an arithmetic number, because the mean of its divisors is an integer number (520800).

Almost surely, 2^20509664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20509664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24998400).

20509664 is an abundant number, since it is smaller than the sum of its proper divisors (29487136).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20509664 is a wasteful number, since it uses less digits than its factorization.

20509664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 176 (or 168 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 32.

The square root of 20509664 is about 4528.7596535917. The cubic root of 20509664 is about 273.7281833840.

The spelling of 20509664 in words is "twenty million, five hundred nine thousand, six hundred sixty-four".