643680 has 96 divisors (see below), whose sum is σ = 2268000. Its totient is φ = 170496.

The previous prime is 643661. The next prime is 643681. The reversal of 643680 is 86346.

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

It is a Harshad number since it is a multiple of its sum of digits (27).

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 643680.

It is not an unprimeable number, because it can be changed into a prime (643681) by changing a digit.

643680 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, 4246 + ... + 4394.

It is an arithmetic number, because the mean of its divisors is an integer number (23625).

2⁶⁴³⁶⁸⁰ is an apocalyptic number.

643680 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 643680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1134000).

643680 is an abundant number, since it is smaller than the sum of its proper divisors (1624320).

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

643680 is a wasteful number, since it uses less digits than its factorization.

643680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173 (or 159 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 643680 is about 802.2967032214. The cubic root of 643680 is about 86.3422453527.

The spelling of 643680 in words is "six hundred forty-three thousand, six hundred eighty".