640967904 has 144 divisors (see below), whose sum is σ = 1951971840. Its totient is φ = 206686080.

The previous prime is 640967897. The next prime is 640967939. The reversal of 640967904 is 409769046.

It is a tau number, because it is divible by the number of its divisors (144).

It is a self number, because there is not a number n which added to its sum of digits gives 640967904.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 239727 + ... + 242385.

It is an arithmetic number, because the mean of its divisors is an integer number (13555360).

Almost surely, 2^640967904 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 640967904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (975985920).

640967904 is an abundant number, since it is smaller than the sum of its proper divisors (1311003936).

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

640967904 is a wasteful number, since it uses less digits than its factorization.

640967904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2715 (or 2695 counting only the distinct ones).

The product of its (nonzero) digits is 326592, while the sum is 45.

The square root of 640967904 is about 25317.3439365191. The cubic root of 640967904 is about 862.2080917647.

The spelling of 640967904 in words is "six hundred forty million, nine hundred sixty-seven thousand, nine hundred four".