640704 has 56 divisors (see below), whose sum is σ = 1755648. Its totient is φ = 206080.

The previous prime is 640691. The next prime is 640727. The reversal of 640704 is 407046.

640704 is a modest number, since divided by 704 gives 64 as remainder.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640704.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8989 + ... + 9059.

2⁶⁴⁰⁷⁰⁴ is an apocalyptic number.

640704 is a gapful number since it is divisible by the number (64) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640704, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (877824).

640704 is an abundant number, since it is smaller than the sum of its proper divisors (1114944).

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

640704 is a wasteful number, since it uses less digits than its factorization.

640704 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133 (or 123 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 21.

The square root of 640704 is about 800.4398790665. The cubic root of 640704 is about 86.2089743977.

The spelling of 640704 in words is "six hundred forty thousand, seven hundred four".