20661664 has 48 divisors (see below), whose sum is σ = 45360000. Its totient is φ = 9206784.

The previous prime is 20661643. The next prime is 20661689. The reversal of 20661664 is 46616602.

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 9337 + ... + 11335.

It is an arithmetic number, because the mean of its divisors is an integer number (945000).

Almost surely, 2^20661664 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 20661664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22680000).

20661664 is an abundant number, since it is smaller than the sum of its proper divisors (24698336).

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

20661664 is a wasteful number, since it uses less digits than its factorization.

20661664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2045 (or 2037 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 31.

The square root of 20661664 is about 4545.5103123852. The cubic root of 20661664 is about 274.4027323944.

The spelling of 20661664 in words is "twenty million, six hundred sixty-one thousand, six hundred sixty-four".