643961040 has 80 divisors (see below), whose sum is σ = 2003847936. Its totient is φ = 171072000.

The previous prime is 643961033. The next prime is 643961057. The reversal of 643961040 is 40169346.

643961040 is digitally balanced in base 6, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (80).

It is a junction number, because it is equal to n+sod(n) for n = 643960992 and 643961010.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 60090 + ... + 69990.

Almost surely, 2^643961040 is an apocalyptic number.

643961040 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 643961040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1001923968).

643961040 is an abundant number, since it is smaller than the sum of its proper divisors (1359886896).

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

643961040 is a wasteful number, since it uses less digits than its factorization.

643961040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10188 (or 10182 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 33.

The square root of 643961040 is about 25376.3874497534. The cubic root of 643961040 is about 863.5480961548.

The spelling of 643961040 in words is "six hundred forty-three million, nine hundred sixty-one thousand, forty".