643643766 has 64 divisors (see below), whose sum is σ = 1543147200. Its totient is φ = 198102528.

The previous prime is 643643743. The next prime is 643643773. The reversal of 643643766 is 667346346.

It is a super-3 number, since 3×643643766³ (a number of 27 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 42040 + ... + 55268.

It is an arithmetic number, because the mean of its divisors is an integer number (24111675).

Almost surely, 2^643643766 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 643643766, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (771573600).

643643766 is an abundant number, since it is smaller than the sum of its proper divisors (899503434).

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

643643766 is a wasteful number, since it uses less digits than its factorization.

643643766 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13310 (or 13304 counting only the distinct ones).

The product of its digits is 1306368, while the sum is 45.

The square root of 643643766 is about 25370.1353169430. The cubic root of 643643766 is about 863.4062519800.

The spelling of 643643766 in words is "six hundred forty-three million, six hundred forty-three thousand, seven hundred sixty-six".