645615664 has 40 divisors (see below), whose sum is σ = 1360279008. Its totient is φ = 295603200.

The previous prime is 645615653. The next prime is 645615667. The reversal of 645615664 is 466516546.

It is a Smith number, since the sum of its digits (43) coincides with the sum of the digits of its prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 645615664.

It is not an unprimeable number, because it can be changed into a prime (645615667) 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 7 ways as a sum of consecutive naturals, for example, 22012 + ... + 42139.

Almost surely, 2^645615664 is an apocalyptic number.

It is an amenable number.

645615664 is an abundant number, since it is smaller than the sum of its proper divisors (714663344).

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

645615664 is a wasteful number, since it uses less digits than its factorization.

645615664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64213 (or 64207 counting only the distinct ones).

The product of its digits is 518400, while the sum is 43.

The square root of 645615664 is about 25408.9681805460. The cubic root of 645615664 is about 864.2870773859.

It can be divided in two parts, 64561 and 5664, that added together give a square (70225 = 265²).

The spelling of 645615664 in words is "six hundred forty-five million, six hundred fifteen thousand, six hundred sixty-four".