1605521664 has 108 divisors (see below), whose sum is σ = 4788938700. Its totient is φ = 516698112.

The previous prime is 1605521663. The next prime is 1605521699. The reversal of 1605521664 is 4661255061.

It can be written as a sum of positive squares in 2 ways, for example, as 1369592064 + 235929600 = 37008^2 + 15360^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (1605521663) 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 11 ways as a sum of consecutive naturals, for example, 54802 + ... + 78830.

It is an arithmetic number, because the mean of its divisors is an integer number (44342025).

Almost surely, 2^1605521664 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 1605521664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2394469350).

1605521664 is an abundant number, since it is smaller than the sum of its proper divisors (3183417036).

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

1605521664 is a wasteful number, since it uses less digits than its factorization.

1605521664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24080 (or 24063 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 36.

The square root of 1605521664 is about 40068.9613541454. The cubic root of 1605521664 is about 1170.9510041310.

The spelling of 1605521664 in words is "one billion, six hundred five million, five hundred twenty-one thousand, six hundred sixty-four".