643940 has 24 divisors (see below), whose sum is σ = 1475712. Its totient is φ = 234080.

The previous prime is 643927. The next prime is 643949. The reversal of 643940 is 49346.

643940 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a d-powerful number, because it can be written as 6⁶ + 4³ + 9⁶ + 3⁵ + 4⁸ + 0 .

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 643940.

It is not an unprimeable number, because it can be changed into a prime (643949) by changing a digit.

643940 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 7 ways as a sum of consecutive naturals, for example, 1244 + ... + 1683.

It is an arithmetic number, because the mean of its divisors is an integer number (61488).

2⁶⁴³⁹⁴⁰ is an apocalyptic number.

It is an amenable number.

643940 is an abundant number, since it is smaller than the sum of its proper divisors (831772).

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

643940 is a wasteful number, since it uses less digits than its factorization.

643940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2947 (or 2945 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 26.

The square root of 643940 is about 802.4587216798. The cubic root of 643940 is about 86.3538691212.

It can be divided in two parts, 64 and 3940, that added together give a palindrome (4004).

The spelling of 643940 in words is "six hundred forty-three thousand, nine hundred forty".