645447664 has 20 divisors (see below), whose sum is σ = 1293678360. Its totient is φ = 311595200.

The previous prime is 645447661. The next prime is 645447667. The reversal of 645447664 is 466744546.

It is an interprime number because it is at equal distance from previous prime (645447661) and next prime (645447667).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645447661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 695062 + ... + 695989.

It is an arithmetic number, because the mean of its divisors is an integer number (64683918).

Almost surely, 2^645447664 is an apocalyptic number.

It is an amenable number.

645447664 is an abundant number, since it is smaller than the sum of its proper divisors (648230696).

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

645447664 is a wasteful number, since it uses less digits than its factorization.

645447664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1391088 (or 1391082 counting only the distinct ones).

The product of its digits is 1935360, while the sum is 46.

The square root of 645447664 is about 25405.6620460873. The cubic root of 645447664 is about 864.2121035620.

The spelling of 645447664 in words is "six hundred forty-five million, four hundred forty-seven thousand, six hundred sixty-four".