643911768 has 80 divisors (see below), whose sum is σ = 1808814480. Its totient is φ = 214011072.

The previous prime is 643911761. The next prime is 643911809. The reversal of 643911768 is 867119346.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (643911761) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 256005 + ... + 258507.

It is an arithmetic number, because the mean of its divisors is an integer number (22610181).

Almost surely, 2^643911768 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 643911768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (904407240).

643911768 is an abundant number, since it is smaller than the sum of its proper divisors (1164902712).

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

643911768 is a wasteful number, since it uses less digits than its factorization.

643911768 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2918 (or 2905 counting only the distinct ones).

The product of its digits is 217728, while the sum is 45.

The square root of 643911768 is about 25375.4166074175. The cubic root of 643911768 is about 863.5260711024.

The spelling of 643911768 in words is "six hundred forty-three million, nine hundred eleven thousand, seven hundred sixty-eight".