643963890 has 64 divisors (see below), whose sum is σ = 1617739776. Its totient is φ = 163745472.

The previous prime is 643963877. The next prime is 643963909. The reversal of 643963890 is 98369346.

643963890 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 251959 + ... + 254501.

It is an arithmetic number, because the mean of its divisors is an integer number (25277184).

Almost surely, 2^643963890 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 643963890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (808869888).

643963890 is an abundant number, since it is smaller than the sum of its proper divisors (973775886).

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

643963890 is a wasteful number, since it uses less digits than its factorization.

643963890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2943.

The product of its (nonzero) digits is 839808, while the sum is 48.

The square root of 643963890 is about 25376.4436042563. The cubic root of 643963890 is about 863.5493700976.

It can be divided in two parts, 64396 and 3890, that added together give a palindrome (68286).

The spelling of 643963890 in words is "six hundred forty-three million, nine hundred sixty-three thousand, eight hundred ninety".