643961760 has 192 divisors, whose sum is σ = 2255662080. Its totient is φ = 153354240.

The previous prime is 643961741. The next prime is 643961761. The reversal of 643961760 is 67169346.

It is not an unprimeable number, because it can be changed into a prime (643961761) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 191776 + ... + 195104.

It is an arithmetic number, because the mean of its divisors is an integer number (11748240).

Almost surely, 2^643961760 is an apocalyptic number.

643961760 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 643961760, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1127831040).

643961760 is an abundant number, since it is smaller than the sum of its proper divisors (1611700320).

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

643961760 is a wasteful number, since it uses less digits than its factorization.

643961760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3391 (or 3383 counting only the distinct ones).

The product of its (nonzero) digits is 163296, while the sum is 42.

The square root of 643961760 is about 25376.4016361658. The cubic root of 643961760 is about 863.5484179934.

The spelling of 643961760 in words is "six hundred forty-three million, nine hundred sixty-one thousand, seven hundred sixty".