643971858 has 16 divisors (see below), whose sum is σ = 1299342816. Its totient is φ = 212757440.

The previous prime is 643971857. The next prime is 643971893. The reversal of 643971858 is 858179346.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 643971858.

It is not an unprimeable number, because it can be changed into a prime (643971857) 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 7 ways as a sum of consecutive naturals, for example, 474228 + ... + 475583.

It is an arithmetic number, because the mean of its divisors is an integer number (81208926).

Almost surely, 2^643971858 is an apocalyptic number.

643971858 is an abundant number, since it is smaller than the sum of its proper divisors (655370958).

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

643971858 is a wasteful number, since it uses less digits than its factorization.

643971858 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 949929.

The product of its digits is 1451520, while the sum is 51.

The square root of 643971858 is about 25376.6005997651. The cubic root of 643971858 is about 863.5529317533.

The spelling of 643971858 in words is "six hundred forty-three million, nine hundred seventy-one thousand, eight hundred fifty-eight".