643766400 has 192 divisors, whose sum is σ = 2356322400. Its totient is φ = 171648000.

The previous prime is 643766371. The next prime is 643766423. The reversal of 643766400 is 4667346.

643766400 is a `hidden beast` number, since 6 + 4 + 3 + 7 + 6 + 640 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (192).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 82675 + ... + 90125.

Almost surely, 2^643766400 is an apocalyptic number.

643766400 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 643766400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1178161200).

643766400 is an abundant number, since it is smaller than the sum of its proper divisors (1712556000).

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

643766400 is a wasteful number, since it uses less digits than its factorization.

643766400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7484 (or 7461 counting only the distinct ones).

The product of its (nonzero) digits is 72576, while the sum is 36.

The square root of 643766400 is about 25372.5520986755. The cubic root of 643766400 is about 863.4610836762.

The spelling of 643766400 in words is "six hundred forty-three million, seven hundred sixty-six thousand, four hundred".