643660 has 12 divisors (see below), whose sum is σ = 1351728. Its totient is φ = 257456.

The previous prime is 643651. The next prime is 643661. The reversal of 643660 is 66346.

It is a happy number.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (643661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16072 + ... + 16111.

It is an arithmetic number, because the mean of its divisors is an integer number (112644).

2⁶⁴³⁶⁶⁰ is an apocalyptic number.

It is an amenable number.

643660 is an abundant number, since it is smaller than the sum of its proper divisors (708068).

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

643660 is a wasteful number, since it uses less digits than its factorization.

643660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32192 (or 32190 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 25.

The square root of 643660 is about 802.2842389079. The cubic root of 643660 is about 86.3413510871.

The spelling of 643660 in words is "six hundred forty-three thousand, six hundred sixty".