643521336 has 64 divisors (see below), whose sum is σ = 1725494400. Its totient is φ = 199375488.

The previous prime is 643521331. The next prime is 643521371. The reversal of 643521336 is 633125346.

It is a junction number, because it is equal to n+sod(n) for n = 643521297 and 643521306.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643521331) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10855 + ... + 37481.

It is an arithmetic number, because the mean of its divisors is an integer number (26960850).

Almost surely, 2^643521336 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 643521336, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (862747200).

643521336 is an abundant number, since it is smaller than the sum of its proper divisors (1081973064).

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

643521336 is a wasteful number, since it uses less digits than its factorization.

643521336 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26708 (or 26704 counting only the distinct ones).

The product of its digits is 38880, while the sum is 33.

The square root of 643521336 is about 25367.7223258218. The cubic root of 643521336 is about 863.3515045477.

The spelling of 643521336 in words is "six hundred forty-three million, five hundred twenty-one thousand, three hundred thirty-six".