643499621856 has 1152 divisors, whose sum is σ = 2427636556800. Its totient is φ = 166577596416.

The previous prime is 643499621801. The next prime is 643499621903. The reversal of 643499621856 is 658126994346.

643499621856 is a `hidden beast` number, since 6 + 4 + 3 + 499 + 62 + 1 + 85 + 6 = 666.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a junction number, because it is equal to n+sod(n) for n = 643499621793 and 643499621802.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 2323103190 + ... + 2323103466.

It is an arithmetic number, because the mean of its divisors is an integer number (2107323400).

Almost surely, 2^643499621856 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 643499621856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1213818278400).

643499621856 is an abundant number, since it is smaller than the sum of its proper divisors (1784136934944).

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

643499621856 is a wasteful number, since it uses less digits than its factorization.

643499621856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 403 (or 369 counting only the distinct ones).

The product of its digits is 67184640, while the sum is 63.

The spelling of 643499621856 in words is "six hundred forty-three billion, four hundred ninety-nine million, six hundred twenty-one thousand, eight hundred fifty-six".