643655040 has 256 divisors, whose sum is σ = 2377105920. Its totient is φ = 145096704.

The previous prime is 643655011. The next prime is 643655041. The reversal of 643655040 is 40556346.

It is a junction number, because it is equal to n+sod(n) for n = 643654992 and 643655010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643655041) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1115232 + ... + 1115808.

It is an arithmetic number, because the mean of its divisors is an integer number (9285570).

Almost surely, 2^643655040 is an apocalyptic number.

643655040 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 643655040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1188552960).

643655040 is an abundant number, since it is smaller than the sum of its proper divisors (1733450880).

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

643655040 is a wasteful number, since it uses less digits than its factorization.

643655040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 689 (or 677 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 33.

The square root of 643655040 is about 25370.3575063498. The cubic root of 643655040 is about 863.4112930632.

The spelling of 643655040 in words is "six hundred forty-three million, six hundred fifty-five thousand, forty".