643872 has 48 divisors (see below), whose sum is σ = 1784160. Its totient is φ = 202752.

The previous prime is 643859. The next prime is 643873. The reversal of 643872 is 278346.

It is a tau number, because it is divible by the number of its divisors (48).

It is not an unprimeable number, because it can be changed into a prime (643873) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1648 + ... + 2000.

It is an arithmetic number, because the mean of its divisors is an integer number (37170).

2⁶⁴³⁸⁷² 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 643872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (892080).

643872 is an abundant number, since it is smaller than the sum of its proper divisors (1140288).

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

643872 is a wasteful number, since it uses less digits than its factorization.

643872 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 385 (or 377 counting only the distinct ones).

The product of its digits is 8064, while the sum is 30.

The square root of 643872 is about 802.4163507806. The cubic root of 643872 is about 86.3508293609.

The spelling of 643872 in words is "six hundred forty-three thousand, eight hundred seventy-two".