640680 has 64 divisors (see below), whose sum is σ = 2030400. Its totient is φ = 161280.

The previous prime is 640669. The next prime is 640687. The reversal of 640680 is 86046.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 640680.

It is not an unprimeable number, because it can be changed into a prime (640687) by changing a digit.

640680 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2140 + ... + 2420.

It is an arithmetic number, because the mean of its divisors is an integer number (31725).

2⁶⁴⁰⁶⁸⁰ is an apocalyptic number.

640680 is a gapful number since it is divisible by the number (60) 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 640680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1015200).

640680 is an abundant number, since it is smaller than the sum of its proper divisors (1389720).

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

640680 is a wasteful number, since it uses less digits than its factorization.

640680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 314 (or 310 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 640680 is about 800.4248871693. The cubic root of 640680 is about 86.2078979562.

The spelling of 640680 in words is "six hundred forty thousand, six hundred eighty".