643406400 has 504 divisors, whose sum is σ = 2820277824. Its totient is φ = 135475200.

The previous prime is 643406299. The next prime is 643406419. The reversal of 643406400 is 4604346.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (504).

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 1310155 + ... + 1310645.

Almost surely, 2^643406400 is an apocalyptic number.

643406400 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 643406400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1410138912).

643406400 is an abundant number, since it is smaller than the sum of its proper divisors (2176871424).

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

643406400 is a wasteful number, since it uses less digits than its factorization.

643406400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 539 (or 521 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 27.

The square root of 643406400 is about 25365.4568261642. The cubic root of 643406400 is about 863.3001019129.

The spelling of 643406400 in words is "six hundred forty-three million, four hundred six thousand, four hundred".