643765920 has 288 divisors, whose sum is σ = 2391088896. Its totient is φ = 145152000.

The previous prime is 643765919. The next prime is 643765937. The reversal of 643765920 is 29567346.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2375385 + ... + 2375655.

It is an arithmetic number, because the mean of its divisors is an integer number (8302392).

Almost surely, 2^643765920 is an apocalyptic number.

643765920 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 643765920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1195544448).

643765920 is an abundant number, since it is smaller than the sum of its proper divisors (1747322976).

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

643765920 is a wasteful number, since it uses less digits than its factorization.

643765920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 404 (or 389 counting only the distinct ones).

The product of its (nonzero) digits is 272160, while the sum is 42.

The square root of 643765920 is about 25372.5426396331. The cubic root of 643765920 is about 863.4608690738.

The spelling of 643765920 in words is "six hundred forty-three million, seven hundred sixty-five thousand, nine hundred twenty".