645215664 has 80 divisors (see below), whose sum is σ = 1730246400. Its totient is φ = 206938368.

The previous prime is 645215663. The next prime is 645215677. The reversal of 645215664 is 466512546.

645215664 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (645215663) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 526957 + ... + 528179.

It is an arithmetic number, because the mean of its divisors is an integer number (21628080).

Almost surely, 2^645215664 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 645215664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (865123200).

645215664 is an abundant number, since it is smaller than the sum of its proper divisors (1085030736).

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

645215664 is a wasteful number, since it uses less digits than its factorization.

645215664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1642 (or 1636 counting only the distinct ones).

The product of its digits is 172800, while the sum is 39.

The square root of 645215664 is about 25401.0957243974. The cubic root of 645215664 is about 864.1085468905.

The spelling of 645215664 in words is "six hundred forty-five million, two hundred fifteen thousand, six hundred sixty-four".