645173664 has 96 divisors (see below), whose sum is σ = 1827282240. Its totient is φ = 198561792.

The previous prime is 645173609. The next prime is 645173687. The reversal of 645173664 is 466371546.

It is a tau number, because it is divible by the number of its divisors (96).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 82767 + ... + 90225.

It is an arithmetic number, because the mean of its divisors is an integer number (19034190).

Almost surely, 2^645173664 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 645173664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (913641120).

645173664 is an abundant number, since it is smaller than the sum of its proper divisors (1182108576).

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

645173664 is a wasteful number, since it uses less digits than its factorization.

645173664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7542 (or 7534 counting only the distinct ones).

The product of its digits is 362880, while the sum is 42.

The square root of 645173664 is about 25400.2689749538. The cubic root of 645173664 is about 864.0897969084.

The spelling of 645173664 in words is "six hundred forty-five million, one hundred seventy-three thousand, six hundred sixty-four".