643900 has 36 divisors (see below), whose sum is σ = 1437408. Its totient is φ = 250240.

The previous prime is 643889. The next prime is 643919. The reversal of 643900 is 9346.

It is an Ulam number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4632 + ... + 4768.

It is an arithmetic number, because the mean of its divisors is an integer number (39928).

2⁶⁴³⁹⁰⁰ 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 643900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (718704).

643900 is an abundant number, since it is smaller than the sum of its proper divisors (793508).

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

643900 is a wasteful number, since it uses less digits than its factorization.

643900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198 (or 191 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 22.

The square root of 643900 is about 802.4337978924. The cubic root of 643900 is about 86.3520810528.

The spelling of 643900 in words is "six hundred forty-three thousand, nine hundred".